I've never noticed any difference in fuel economy driving on the motorway with Windows opened or closed.
I like air con to cool the car leather interior quickly before getting in it, but I also like driving with the windows open, and icy cold air blasting my feet and legs
I think Mythbusters did a test like this some time ago, can't remember the outcome.
But I think at slow engine revs such as during town driving, opening the window and switching off AC gives the best results - open windows wont affect drag much at those speeds but turning on AC at low revs will make it work harder.
At higher speeds such as motorway driving, close the windows and turn on the AC - open windows will have a greater effect on wind resistance at higher speeds but turning on the AC while the engine is already at say 2000 revs wont result in the engine having to do much additional work.
Apparently 40mph is the cut-off point. Slower than that it's more fuel efficient to have the windows open, faster windows closed and AC ON.
Apparently 40mph is the cut-off point. Slower than that it's more fuel efficient to have the windows open, faster windows closed and AC ON.
It'll probably vary considerably from vehicle to vehicle - cars with a bigger engine will notice it less when the AC is switched on. And some vehicles wont have their drag factor increased all that much when the windows are opened.
There's a few varying factors involved and it would be interesting if some definitive figures could be obtained as I'd be quite interested in them.
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My garage test the system first to check that it's not leaking.
I like air con to cool the car leather interior quickly before getting in it, but I also like driving with the windows open, and icy cold air blasting my feet and legs
Apparently 40mph is the cut-off point. Slower than that it's more fuel efficient to have the windows open, faster windows closed and AC ON.
It'll probably vary considerably from vehicle to vehicle - cars with a bigger engine will notice it less when the AC is switched on. And some vehicles wont have their drag factor increased all that much when the windows are opened.
There's a few varying factors involved and it would be interesting if some definitive figures could be obtained as I'd be quite interested in them.