# Significant fuel economy (MPG) decrease



## Heisenburger (Sep 19, 2016)

Over the past month as the average temperatures have quickly skyrocketed well into the 90s (F), my air conditioning has been running non-stop.

My air conditioning seems to be underperforming (feels less cold than I recall from recent summers) or just generally struggling to keep the mid-day heat at bay. I've been watching the compressor like a hawk and it seems to shut off only once every minute for like 10 seconds before reengaging.

During this same period, my average MPG has decreased noticeably (20% drop - from 29 to 23 MPG). I track this metric closely so I know it's accurate. I don't recall that much of an MPG decrease last few summers. More like 25-26 MPG.

No other running problems.

Vehicle on profile. 251k miles.

Is my AC compressor failing? Other likely culprits?


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## _Tron_ (Feb 9, 2020)

Well, aside from maybe you should check to see if the Ethanol blend has gone up at your local stations, and assuming you are watching your tire pressure, you are on the right track with the A/C. Bring it into a shop that specializes for a basic check. The system may just need to be charged up. Not expensive. And they will check for leaks at the same time.


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## ObeyTheNumbers (7 mo ago)

I can't argue enough for a older, experienced ASE certified mechanic.

Wouldn't have over 440,000 miles on my vehicle without them.


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## Heisenburger (Sep 19, 2016)

_Tron_ said:


> check to see if the Ethanol blend has gone up at your local stations,


I have no doubt that it has, but that's irrelevant to my issue of MPG decrease. The summer blends can only ever increase MPG because they're denser than winter blends.

But I'll check the other ones you mentioned.


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## ObeyTheNumbers (7 mo ago)

Heisenburger said:


> I have no doubt that it has, but that's irrelevant to my issue of MPG decrease. The summer blends can only ever increase MPG because they're denser than winter blends.
> 
> But I'll check the other ones you mentioned.


Our supreme geezer Biden was talking on the news about increasing the ethanol blend to 15% instead of 10%


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## tohunt4me (Nov 23, 2015)

Heisenburger said:


> Over the past month as the average temperatures have quickly skyrocketed well into the 90s (F), my air conditioning has been running non-stop.
> 
> My air conditioning seems to be underperforming (feels less cold than I recall from recent summers) or just generally struggling to keep the mid-day heat at bay. I've been watching the compressor like a hawk and it seems to shut off only once every minute for like 10 seconds before reengaging.
> 
> ...


My home electric bill was $401.00 last month.
Fuel cost increases plus storm repair adjustments from last summers hurricane.

Previous bill was $150.00

Hell it only cost me $600.00 to run a natural gas generator for 45 days during storm & in wake of storm damage. When all power poles &:lines were lying on the ground.

Soon it may be cheaper TO MAKE MY OWN DAMN ELECTRICITY THAN TO BUY IT !


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## tohunt4me (Nov 23, 2015)

ObeyTheNumbers said:


> Our supreme geezer Biden was talking on the news about increasing the ethanol blend to 15% instead of 10%


Biden has allowed/ possibly even " DECREED" BY HIS MAJESTYS " EXECUTIVE PEN" THAT MORE ETHANOL BE USED. LOOK OUT FOR SMOG !
NO SUMMER BLEND.
NO PLANT TURNAROUND WORK & CLOSURES TO SWITCH TO SUMMER BLEND.


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## Heisenburger (Sep 19, 2016)

ObeyTheNumbers said:


> Our supreme geezer Biden was talking on the news about increasing the ethanol blend to 15% instead of 10%


It's exhausting fixing the bullshit that spews from the Twitter firehoses, but again:



> Pure gasoline will give drivers the most miles per gallon, followed by E10 and then E15, but the differences are small. According to the DOE, vehicles will typically go about 3-4% fewer miles per gallon on E10 and 4-5% fewer miles per gallon on E15 compared to pure gasoline.
> 
> That means the difference in *fuel efficiency between E10 and E15 is only about 1-2%*, based on estimates from the DOE and other experts.
> 
> ...


Yes, fuel efficiency is worse with E15 gasoline, but the difference is small

Regardless, I consistently buy E10 only for the past 3 years.


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## Heisenburger (Sep 19, 2016)

Heisenburger said:


> I've been watching the compressor like a hawk and it seems to shut off only once every minute for like 10 seconds before reengaging.


I'm somewhat surprised that nobody has honed in on this particular symptom yet. A compressor that runs/engages 85% of the time. 😧


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## wallae (Jun 11, 2018)

Thinking way back when I flew a gas dc 4 and a dc 6
If they lost that much in fuel economy they would be grounded 
(we had to record fuel burn in climb out, cruise, and decent)


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## Atavar (Aug 11, 2018)

Heisenburger said:


> I have no doubt that it has, but that's irrelevant to my issue of MPG decrease. The summer blends can only ever increase MPG because they're denser than winter blends.
> 
> But I'll check the other ones you mentioned.


More ethanol = worse mpg. I run the cheap stuff in my Odyssey because that’s what the manual says, but on my motorcycle the difference between e10 and e0 is over 20mpg.


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## Atavar (Aug 11, 2018)

Heisenburger said:


> I'm somewhat surprised that nobody has honed in on this particular symptom yet. A compressor that runs/engages 85% of the time. 😧


They have and suggested he get it charged. That may make some difference but unless the compressor is failing (bearings) it shouldn’t make a difference that big. If the compressor were failing he should smell the belt burning.


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## Atavar (Aug 11, 2018)

Heisenburger said:


> Over the past month as the average temperatures have quickly skyrocketed well into the 90s (F), my air conditioning has been running non-stop.
> 
> My air conditioning seems to be underperforming (feels less cold than I recall from recent summers) or just generally struggling to keep the mid-day heat at bay. I've been watching the compressor like a hawk and it seems to shut off only once every minute for like 10 seconds before reengaging.
> 
> ...


Try the simple stuff first. Replace your air filters and pcv valve and change your oil.


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## tohunt4me (Nov 23, 2015)

Atavar said:


> Try the simple stuff first. Replace your air filters and pcv valve and change your oil.


Cabin Air Filter !
Changing it is Important.


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## wallae (Jun 11, 2018)

And don’t forget to change the blinker fluid!


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## Schmanthony (Nov 18, 2017)

Atavar said:


> Try the simple stuff first. Replace your air filters and pcv valve and change your oil.


Air filter? Check it and replace (or clean it) only if dirty. PCV? Inspect/test before replacing. Unless it's very cheap and easy to replace and you know it's very old. Oil change? They are important to keep up with for sure, but putting them off will not affect fuel economy.

Other things that will affect fuel economy? Ignition! Check plugs, coils, look for spark. Fuel pressure! Check both at idle and while under load.Compression! check both max pressure in each cylinder and also do a leakdown test.


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## observer (Dec 11, 2014)

_Tron_ said:


> Well, aside from maybe you should check to see if the Ethanol blend has gone up at your local stations, and assuming you are watching your tire pressure, you are on the right track with the A/C. Bring it into a shop that specializes for a basic check. The system may just need to be charged up. Not expensive. And they will check for leaks at the same time.


The AC system is under pressure. If the refrigerant were leaking and the system needed charging it wouldn't cool at all because all the refrigerant would have escaped.

If I remember correctly (I took a refrigeration class in college many decades ago), there's a TXV valve in there that somewhere that will sometimes freeze up intermittently and not allow refrigerant to flow. It could also be a faulty temperature sensor.

Whatever it is it needs to be diagnosed by an AC tech.


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## Atavar (Aug 11, 2018)

Schmanthony said:


> Air filter? Check it and replace (or clean it) only if dirty. PCV? Inspect/test before replacing. Unless it's very cheap and easy to replace and you know it's very old. Oil change? They are important to keep up with for sure, but putting them off will not affect fuel economy.
> 
> Other things that will affect fuel economy? Ignition! Check plugs, coils, look for spark. Fuel pressure! Check both at idle and while under load.Compression! check both max pressure in each cylinder and also do a leakdown test.


Air filter and pct are cheap and easy. Always do the simple stuff first. The other things you mentioned are very expensive and time consuming and if bad enough to affect mpg should trigger a check engine light. 
If the OP really suspects the compressor or it’s clutch he could pull the connector from the clutch. The compressor should not turn and in a modern car the information panel will let him know if it affects mpg in just a couple minutes.


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## tohunt4me (Nov 23, 2015)

observer said:


> The AC system is under pressure. If the refrigerant were leaking and the system needed charging it wouldn't cool at all because all the refrigerant would have escaped.
> 
> If I remember correctly (I took a refrigeration class in college many decades ago), there's a TXV valve in there that somewhere that will sometimes freeze up intermittently and not allow refrigerant to flow. It could also be a faulty temperature sensor.
> 
> Whatever it is it needs to be diagnosed by an AC tech.


Change radiator coolant !
Radiator cools transmission fluid AND a.c. coolant lines !
Hot weather makes it harder for both to cool !

Clean and straighten radiator fins.
Make sure fins not clogged with bugs,leaves etc.
Change coolant !

















Coolant ratio,level & quality will definantly affect your A.C. ,engine,& transmission.

Check it,fill it, change it with FRESH coolant, maintain it !

Make sure your radiator fans are working.
Make sure your thermostat is working.


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## tohunt4me (Nov 23, 2015)

Coolant is relatively cheap.
Change it every 2-3 years.
Check level. When engine is cold.


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## Schmanthony (Nov 18, 2017)

tohunt4me said:


> Radiator cools transmission fluid AND a.c. coolant lines !


The radiator (engine cooling system) does NOT cool transmission fluid. Often a trans oil cooler is integrated with the radiator assembly, and trans lines are connected to the assembly, but the actual radiator and the coolant are NOT part of the same circuit as the trans lines or trans oil cooler.


tohunt4me said:


> Coolant ratio,level & quality will definantly affect your A.C. ,engine,& transmission.


Nothing about the coolant will affect AC or the transmission. Coolant ONLY cools the engine and provides heat for the passenger compartment, nothing else!

Coolant will also not affect fuel economy, unless maybe your engine is overheating. But if your engine is overheating you've got much bigger problems than worrying about your MPG!


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## Atavar (Aug 11, 2018)

tohunt4me said:


> Change radiator coolant !
> Radiator cools transmission fluid AND a.c. coolant lines !
> Hot weather makes it harder for both to cool !
> 
> ...


The AC does not use coolant. AC is a separate radiator (called a condenser) that cools the high pressure Freon directly. Note that your first and second diagrams are completely separate unrelated systems. If you look behind the grille of your car you will see the small AC condenser _in front of_ the big coolant radiator. You may also see a small transmission cooling radiator which also does not use coolant.


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## Invisible (Jun 15, 2018)

Have you replaced the fuel filter?


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## tohunt4me (Nov 23, 2015)

Atavar said:


> The AC does not use coolant. AC is a separate radiator (called a condenser) that cools the high pressure Freon directly. Note that your first and second diagrams are completely separate unrelated systems. If you look behind the grille of your car you will see the small AC condenser _in front of_ the big coolant radiator. You may also see a small transmission cooling radiator which also does not use coolant.
> View attachment 666943


Still, clean the fins. It's a BUG CATCHER.
MAKE SURE YOUR RADIATOR FAN IS OPERATING.
It draws air through when you are not moving quickly.

If the radiator is hot, the heat will " radiate" to your condenser.

Trust me.
3 weeks ago I had coolant problems
The First symptom was the a.c. not cooling after 8 minutes of driving . Temperature gauge read normal.
Shut the car down, a.c. would operate about 8 minutes then blow hot.

Then the temp..guage shot up. And warning light came on.
Turned on heater & limped home.
Was low coolant.
I had just replaced coolant a year ago.

Can't find any leaks.

Doing fine so far now. Including a.c.

I was worried it might be a head gasket.
No symptoms of that.
Not leaking Anywhere.
Have no idea where the coolant went.


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## tohunt4me (Nov 23, 2015)

Atavar said:


> The AC does not use coolant. AC is a separate radiator (called a condenser) that cools the high pressure Freon directly. Note that your first and second diagrams are completely separate unrelated systems. If you look behind the grille of your car you will see the small AC condenser _in front of_ the big coolant radiator. You may also see a small transmission cooling radiator which also does not use coolant.
> View attachment 666943


Specific transmission coolers are a part of a " Heavy Duty " package.
Taxi,police,towing vehicles.
You can add your own transmission cooler aftermarket.
Also you can add engine oil cooler.

Stock cars run lines through the radiator .


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## tohunt4me (Nov 23, 2015)

In front wheel drive cars, everything is more compact.
Heat sources all close together.

Rear wheel drive transmission line pictured here.
More tubing for cooling & transmission further from engine in rear wheel drive.


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## tohunt4me (Nov 23, 2015)

You can buy specialty oil coolers & transmission oil coolers . You can buy transmission pans that allow extra capacity & have cooling fins
More volume helps.
















Hell . . . Some people used to run a " summer thermostat" & a winter thermostat. Summer thermostat should open [email protected] about 20° cooler.

They used to be easier to reach.

The old folks used to keep their off season thermostat hanging on a nail in the garage.


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## Heisenburger (Sep 19, 2016)

Atavar said:


> suggested he get it charged


✅Charged in June. Verified in July.



Atavar said:


> If the compressor were failing he should smell the belt burning


✅ no odd smell whatsoever, serpentine belt has about 60k miles and passed visual inspection



Atavar said:


> Try the simple stuff first. Replace your air filters and pcv valve and change your oil.


✅



tohunt4me said:


> Cabin Air Filter !
> Changing it is Important.


✅ not equipped



wallae said:


> And don’t forget to change the blinker fluid!


✅✅✅I back flush and fill it and replace its inline filter every 1,000 miles...is that sufficient? 



Schmanthony said:


> Air filter? Check it and replace (or clean it) only if dirty. PCV? Inspect/test before replacing. Unless it's very cheap and easy to replace and you know it's very old. Oil change? They are important to keep up with for sure, but putting them off will not affect fuel economy.
> 
> Other things that will affect fuel economy? Ignition! Check plugs, coils, look for spark. Fuel pressure! Check both at idle and while under load.Compression! check both max pressure in each cylinder and also do a leakdown test.


 Thanks.



Atavar said:


> he could pull the connector from the clutch.


 I just turn off AC switch itself. Same effect.



tohunt4me said:


> Make sure your radiator fans are working.


✅



tohunt4me said:


> Make sure your thermostat is working.


 I need to do this. But wouldn't that show up on the instrument panel temperature gauge?



Invisible said:


> Have you replaced the fuel filter?


No. But two years and 50k miles ago, that section was checked thoroughly by ASE technician. Something cheap in that area was found malfunctioning and replaced but not the filter itself because it checked out fine.


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## Heisenburger (Sep 19, 2016)

_Tron_ said:


> you should check to see if the Ethanol blend has gone up at your local stations


They can't legally change the blend in the gas station's tanks without relabeling.


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## NoPool4Me (Apr 16, 2018)

tohunt4me said:


> My home electric bill was $401.00 last month.
> Fuel cost increases plus storm repair adjustments from last summers hurricane.
> 
> Previous bill was $150.00
> ...


What is the average temperature you keep your AC at?


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## tohunt4me (Nov 23, 2015)

NoPool4Me said:


> What is the average temperature you keep your AC at?


I admit I have 24/7 home healthcare here for a relative & they love to freeze it out on my dime.

Yet this bill is over double of the last one under roughly the same circumstances


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## tohunt4me (Nov 23, 2015)

Heisenburger said:


> They can't legally change the blend in th
> 
> 
> 
> ...


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## nj9000 (Jun 6, 2019)

Heisenburger said:


> I'm somewhat surprised that nobody has honed in on this particular symptom yet. A compressor that runs/engages 85% of the time. 😧


As an a/c ages it'll become less efficient, possibly due to losing refrigerant but it can also be from other causes. It'll cycle the compressor to try and achieve a certain temperature, and if it struggles achieving that it'll run the compressor a lot more. If its constantly going, then in your house a/c you'll see your electric bill skyrocket. In your car, likewise it'll use a lot more fuel. I know on window air conditioners you have to clean the coils of dust or else it'll struggle for airflow and the compressor will run a lot. When the a-coil on my house a/c was failing a few years ago my power bill went up because of the compressor having to run more. Topping it up on refrigerant helped, and ended up getting the a-coil replaced and the system tuned up and with it running properly it cycles on less often and uses less electricity. IIRC compressors (at least on house hvac) don't fail very often. With around 250k miles on your car if you haven't gotten it serviced its probably time, and you're real lucky it hasn't needed it so far.

edit: someone here mentioned that when a/c systems leak, they just lose all their refrigerant all at once and won't cool. That wasn't my experience with my house a/c. It lost a little bit over a few years, then it got to a point where an a/c tech could top it off and it'd last a full season. I've also had that happen with auto a/c, it just slowly lose it and not cool as well over time.


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## nj9000 (Jun 6, 2019)

Schmanthony said:


> The radiator (engine cooling system) does NOT cool transmission fluid. Often a trans oil cooler is integrated with the radiator assembly, and trans lines are connected to the assembly, but the actual radiator and the coolant are NOT part of the same circuit as the trans lines or trans oil cooler.
> 
> Nothing about the coolant will affect AC or the transmission. Coolant ONLY cools the engine and provides heat for the passenger compartment, nothing else!
> 
> Coolant will also not affect fuel economy, unless maybe your engine is overheating. But if your engine is overheating you've got much bigger problems than worrying about your MPG!


Eh, not exactly true. The a/c cools by sending heat to the condenser which is bundled with the radiator at the front of the car. The hotter your car is running, the hotter your radiator, your condenser will not be as efficient getting rid of heat and your a/c won't work as well. So you want your cooling system performing properly. 

Having driven older shit boxes when I was in college, if your temp gauge starts going up on an older car, you turn off the a/c so its not adding more heat to the radiator making the engine struggle to cool. That effect also goes the other way to some degree, ie the heat of the radiator affecting the condenser.


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## Heisenburger (Sep 19, 2016)

Yes, I'm aware of that EO. That was not a "must do" order. It merely makes it legal to *optionally* sell E15 in the summer in addition to the rest of the year.

Regardless, retail gas stations historically selling E10 can just simply keep doing so (hence the pic of the sticker on the gas pump dated today).


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## Heisenburger (Sep 19, 2016)

> Only 2,300 US gas stations—about 1.5% of the country’s roughly 150,000 fueling stations—sell E15 gas. The remaining 98.5% of gas stations may not have the proper equipment (pdf) to safely store E15.


Biden’s approval of E15 gas will only affect 1.5% of gas stations


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## Heisenburger (Sep 19, 2016)

How rare is E15?

Only one station in my ZIP code has it. About a dozen in the entire Atlanta metropolitan area serving about 6 million people and 3 million vehicles.



> Yet, the issue in Atlanta is where to find it. According to E85prices.com, a site that tracks the cost and availability of alternative fuel, there are 10 gas stations selling E15 in Georgia. Seven of them are in metro Atlanta.


Finding cheaper E15 gasoline in Georgia is a challenge


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## Atavar (Aug 11, 2018)

nj9000 said:


> Eh, not exactly true. The a/c cools by sending heat to the condenser which is bundled with the radiator at the front of the car. The hotter your car is running, the hotter your radiator, your condenser will not be as efficient getting rid of heat and your a/c won't work as well. So you want your cooling system performing properly.
> 
> Having driven older shit boxes when I was in college, if your temp gauge starts going up on an older car, you turn off the a/c so its not adding more heat to the radiator making the engine struggle to cool. That effect also goes the other way to some degree, ie the heat of the radiator affecting the condenser.


The A/C reduces the cooling of the radiator because the condenser is in front of the radiator and air flowing through it is warmed before it gets to the radiator. The reverse is not true unless your fan is turning backwards. The radiator does not heat the condenser.


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## observer (Dec 11, 2014)

nj9000 said:


> As an a/c ages it'll become less efficient, possibly due to losing refrigerant but it can also be from other causes. It'll cycle the compressor to try and achieve a certain temperature, and if it struggles achieving that it'll run the compressor a lot more. If its constantly going, then in your house a/c you'll see your electric bill skyrocket. In your car, likewise it'll use a lot more fuel. I know on window air conditioners you have to clean the coils of dust or else it'll struggle for airflow and the compressor will run a lot. When the a-coil on my house a/c was failing a few years ago my power bill went up because of the compressor having to run more. Topping it up on refrigerant helped, and ended up getting the a-coil replaced and the system tuned up and with it running properly it cycles on less often and uses less electricity. IIRC compressors (at least on house hvac) don't fail very often. With around 250k miles on your car if you haven't gotten it serviced its probably time, and you're real lucky it hasn't needed it so far.
> 
> edit: someone here mentioned that when a/c systems leak, they just lose all their refrigerant all at once and won't cool. That wasn't my experience with my house a/c. It lost a little bit over a few years, then it got to a point where an a/c tech could top it off and it'd last a full season. I've also had that happen with auto a/c, it just slowly lose it and not cool as well over time.





nj9000 said:


> As an a/c ages it'll become less efficient, possibly due to losing refrigerant but it can also be from other causes. It'll cycle the compressor to try and achieve a certain temperature, and if it struggles achieving that it'll run the compressor a lot more. If its constantly going, then in your house a/c you'll see your electric bill skyrocket. In your car, likewise it'll use a lot more fuel. I know on window air conditioners you have to clean the coils of dust or else it'll struggle for airflow and the compressor will run a lot. When the a-coil on my house a/c was failing a few years ago my power bill went up because of the compressor having to run more. Topping it up on refrigerant helped, and ended up getting the a-coil replaced and the system tuned up and with it running properly it cycles on less often and uses less electricity. IIRC compressors (at least on house hvac) don't fail very often. With around 250k miles on your car if you haven't gotten it serviced its probably time, and you're real lucky it hasn't needed it so far.
> 
> edit: someone here mentioned that when a/c systems leak, they just lose all their refrigerant all at once and won't cool. That wasn't my experience with my house a/c. It lost a little bit over a few years, then it got to a point where an a/c tech could top it off and it'd last a full season. I've also had that happen with auto a/c, it just slowly lose it and not cool as well over time.


An AC system is pressurized at around 30 PSI on the low side (suction) and 200-250 PSI on the high side (discharge).

That's the equivalent of a regular pressurized tire and a tire pressurized to 7 to 8 times a regular tire.

If you have a leak in a pressurized tire, YOU WILL EVENTUALLY RUN OUT OF AIR. At 7 to 8 times the pressure of a regular tire you will QUICKLY run out of air.

There is no such thing as topping off refrigerant. There is a predetermined amount of refrigerant in each system designed by the manufacturer. No more, no less is needed.

To be properly serviced, an AC system must be vacuumed out. Newer AC recovery systems automatically filter the refrigerant and WEIGH it to see how much refrigerant was present.

At a previous job, one of my responsibilities was comparing recovery rates of materials per vehicle. Copper radiators, aluminum radiators, aluminum wheels, Aluminum motors. Copper wire, Etc. Etc. Etc. and yes, refrigerant per vehicle.

We recycled 25, 30. 35 thousand cars a month and we logged the refrigerant weight and type of every single vehicle. Every pound of refrigerant was separated in to different tanks. R-12 (Freon), R-22, both no longer manufactured in the US and most industrialized nations, (I believe China, India and one or two other countries were allowed a couple more decades of production for their own use but not export) and a mixed tank.

The workers had to be periodically trained and certified to operate the recovery equipment.

By comparing numbers, I could tell which locations were doing a good job recovering refrigerant and which ones were not.

Vehicles had somewhere around 2.8 and 3.5 pounds of refrigerant. The vast majority of vehicles had zero refrigerant.

Back then cars were just beginning to use one serpentine belt. If your AC went out you just removed the AC belt.

What probably fixed your house AC system was the replacement of your A coil.

Topping off your refrigerant was unnecessary and the tech just padded his bill by charging you more for refrigerant he didn't use (unless he did a bad job evacuating the system and let refrigerant escape in to the atmosphere).


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## observer (Dec 11, 2014)

observer said:


> An AC system is pressurized at around 30 PSI on the low side (suction) and 200-250 PSI on the high side (discharge).
> 
> That's the equivalent of a regular pressurized tire and a tire pressurized to 7 to 8 times a regular tire.
> 
> ...


One other thing I forgot, the oil that lubricates the compressor is mixed with the refrigerant. 

Once your refrigerant is gone, your compressor is no longer being lubricated and will fail.


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## nj9000 (Jun 6, 2019)

observer said:


> Topping off your refrigerant was unnecessary and the tech just padded his bill by charging you more for refrigerant he didn't use (unless he did a bad job evacuating the system and let refrigerant escape in to the atmosphere).


Eh, this was like 5 years ago so the memory is a bit hazy. I'm not an a/c or HVAC tech. I watched him do all of it, he seemed to check pressure in the system on one side, it was low, and he topped the refrigerant off until it was the correct pressure? He weighed a tank of R-134 or w/e and charged me for weight. I doubt he swindled me as the temp I measured coming from the vents dropped by like 10F. He did it for a couple seasons until the a-coil completely went out in around 2018. When that was replaced, yeah he vacuumed out the system and gave it the correct weight of refrigerant.


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## Heisenburger (Sep 19, 2016)

nj9000 said:


> As an a/c ages it'll become less efficient, ... It'll cycle the compressor to try and achieve a certain temperature, and if it struggles achieving that it'll run the compressor a lot more. If its constantly going, ... In your car, likewise it'll use a lot more fuel.


I'm settled on this as the explanation: _A gradual deterioration of performance with use._

Black Betty is 14 years old and has seen a hard second life of 80k miles on the mean streets of metro Atlanta in her silver years. She probably has another 12-18 months with me before I put her out to pasture.


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## Heisenburger (Sep 19, 2016)

observer said:


> One other thing I forgot, the oil that lubricates the compressor is mixed with the refrigerant.


But this oil isn't present in the cans of refrigerant when one adds it to a system. So when topping off or recharging with refrigerant alone, the system will be technically low on oil unless one adds oil separately.


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## Heisenburger (Sep 19, 2016)

Heisenburger said:


> Regardless, retail gas stations historically selling E10 can just simply keep doing so (hence the pic of the sticker on the gas pump dated today).


Another gas station today. If they wish to sell E15, they have some relabeling ahead of them.


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## OldBay (Apr 1, 2019)

Heisenburger said:


> Over the past month as the average temperatures have quickly skyrocketed well into the 90s (F), my air conditioning has been running non-stop.
> 
> My air conditioning seems to be underperforming (feels less cold than I recall from recent summers) or just generally struggling to keep the mid-day heat at bay. I've been watching the compressor like a hawk and it seems to shut off only once every minute for like 10 seconds before reengaging.
> 
> ...


Even though I don't like know-it-alls, I will share a trick to increase AC performance dramatically. If that is indeed the problem.

You can buy refridgerant at AutoZone and recharge it yourself for about $25. A car that has a slow leak but that is still blowing coldish, will hold a charge for well over a year. As you add refridgerant, you will notice that it cycles more quickly and that it is blowing colder. 

I had a car that I had to recharge every two years. If you recharge it and it stops blowing cold in weeks/months, then you might look into fixing it. 

The more likely culprit is lower quality gas. When you recharge your ac you can track your mpg to see if it is improved, but my guess is that during the current gas crisis they are blending more ethanol. They usually only mix ethanol in the winter (because mpg is typically better in winter.) But if they are using ethanol in summer, that could explain the drastic loss in mpg.


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## Heisenburger (Sep 19, 2016)

OldBay said:


> Even though I don't like know-it-alls,


I'll gracefully interpret that as a compliment. I don't mind admitting both when I know my material and when I don't.



OldBay said:


> A car that has a slow leak but that is still blowing coldish, will hold a charge for well over a year. As you add refridgerant, you will notice that it cycles more quickly and that it is blowing colder.


Yeah, that's just about what I have been experiencing.



OldBay said:


> but my guess is that during the current gas crisis they are blending more ethanol.


Please see above conversation where we put that to bed with the E15 confusion I helped clear up.


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## OldBay (Apr 1, 2019)

Did you charge your AC? Did it improve? How long did it hold the charge, or are you still enjoying cold AC? How much did it improve your mpg?


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## Heisenburger (Sep 19, 2016)

OldBay said:


> Did you charge your AC?


Yeah.



OldBay said:


> Did it improve?


Very little, but just barely sufficient.



OldBay said:


> How long did it hold the charge, or are you still enjoying cold AC?


Still.



OldBay said:


> How much did it improve your mpg?


None. Still lower than past summer peaks. I suspect it's just working overtime and close to failing. It just stays on virtually non-stop (85-90% of the time).


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## OldBay (Apr 1, 2019)

Did you charge it correctly? When you added fluid, did it start blowing colder and cycle more quickly?


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## Heisenburger (Sep 19, 2016)

OldBay said:


> Did you charge it correctly?


Yes. Exactly as prescribed.



OldBay said:


> When you added fluid, did it start blowing colder and cycle more quickly?


Very little change. Slightly colder. Same cycling.

Fast cycling isn't good.


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