Usually on a smaller car with a smaller engine, turning ON the A/C or using front defrost(which turns on the A/C Compressor) affects MPG pretty bad, how does it affect our trucks? I mean, I know it'll affect it, but how much? Barely noticable or pretty bad?

 

I would say barely if I had to choose. Actually I have seen very little difference in mileage if any at all while running the ac. I think my mileage maybe slightly better in the warmer temps anyway and I know I'm not going to turn off that ac when it gets "Hot" I'm not for sure but I don't think our fuel is winter blended here for cold weather in Texas like up North because it does not get that cold here and stay that way, it could be some what blended though due to people traveling going north. Maybe the slight mileage for me difference could be from warming up of fluids and slightly more idling in the winter.All and all on my truck I'm going to say barely noticeable.

Tony

 

I'd say "somewhat". That's part way between Barely noticeable, and Pretty bad!

 

In the early days of A/C the answer was yes because of type of compressors that were used. With the modern rotarty type compressors, very little. As far as I am concerned the pros out weigh the cons, I love clear windows. Drove to many years with fogged up windows. Mine is never turned off.

 

The answer is no, not at all.
In fact. you will get better MPG with the a/c on and the windows up ,than you would without a/c and windows down.