Originally Posted by bra
My dad got an old Ford F-250 7.3 v8 diesel 1992 and I'll use it during my working schedules only. He told me to use the A/C as I want because it won't affect the MPG. Indeed, he says that because the engine got huge torque...
What do you think? I don't know if its théory is true.
Physics says the compressor uses from 5 - 15 HP to turn it over and compress or pump refrigerant. Your electrical blower (and the clutch on the compressor) increases the electrical load on the alternator making IT use more horsepower.
I am personally still looking for perpetual motion machines and gas tanks that fill themselves magically. I have never found them.
If your fuel mileage is not affected while using your AC then I may want to buy or steal your truck while you are sleeping at night.
I do believe however that when not turned on, your AC will not affect fuel mileage.
What your Dad may mean is that he doesn't detect any increase in fuel usage day to day, because he knows what it uses more or less each week, but then he probably hasn't mounted instrumentation to prove the compressor doesn't increase fuel consumption.
Sorry, I just can't get away from the first and second laws of thermodynamics. They work and apply everywhere else.