Before I turn off the engine, I turn off the A/C; that way when I start the engine the A/C is off and doesn’t contribute any drag to starting the engine. At least that’s my theory. Is there any truth to my thinking?

Possibly on old cars before electronic controls. New cars have a time delay that will not run the A/C compressor until the engine has started.

There goes my bet with my wife. Thanks for the reply. BTW I’m talking about a 1993 Nissan King Cab.

It doesnt matter if you shut it off before or after you shut off the engine just as long as you have it off before you start the engine. While some vehicles will not engage the compressor clutch until after you start the engine and press the A/C button, there are vehicles out there that will have the clutch engaged as soon as the ignition hits the run position meaning it will be engaged while you are cranking the vehicle. I’m not sure about your Nissan though. Either way, what you are doing is fine.


Makes sense to me.

I usually turn off my AC about 5 minutes from home because the air is cool in the cabin and the blower will blow fairly cool air for a bit w/ the ac off.

I never start a cold engine and immediately run the ac. I wait till the engine is completely warmed up then engage the ac.

The tiny, tiny bit of engine wear you may be preventing really doesn’t justify being uncomfortable for a few minutes each time you get in the car, if you ask me. Avoiding high RPMs and hard acceleration on a cold engine is a much bigger factor than your air conditioner.

no difference,waste of time.