Better Gas Mileage with AC/Defrost On?

[GoBucks!]

Over the last year, I've noticed a significant decrease in the gas mileage I've been getting with my V8. It's still within the "normal" range, but much less than previously. I've done all of the typical fixes, but it hasn't changed anything.

I have noticed that I get a couple of more miles per gallon when the AC/Defrost is on versus off. What could this mean. Shouldn't it be the opposite?:loco:

 

[RunnerAK]

Mine is the opposite. I used to leave the defrost on constantly until a member here pointed out that it activates the A/C compressor even though the A/C light doesn't come on. I noticed a slight bump in mileage when I reduced its usage.

If you're in a cold state, it probably has a lot more to do with winter blend gas and a cold engine than the defroster.

 

[preacher35]

Over the last year, I've noticed a significant decrease in the gas mileage I've been getting with my V8. It's still within the "normal" range, but much less than previously. I've done all of the typical fixes, but it hasn't changed anything.

I have noticed that I get a couple of more miles per gallon when the AC/Defrost is on versus off. What could this mean. Shouldn't it be the opposite?:loco:

I have never heard of a vehicle's A/C compressor "increasing" mileage. Compressors put strain on an engine and robs horsepower, not the other way around.

 

[GoBucks!]

It happens in the winter or summer, and there is a definite increase in mileage (about 2 mpg) with the defrost ON. I'm stumped...

 

[m85476585]

Have calculated by hand from the gas pump, or are you just going by the mpg gauge? Either that or use something like a Scangauge

 

[wnelax04sr5]

stuck caliper maybe, the ac could have no bearing on the situation, could be pure coincidence

 

[rich045]

the ac doesnt kill the mpg unless you are idling for a while. the real culprit is driving with the windows open, which causes more drag hence bad gas mileage.