Which is economical? Air Con or window open on motorway?

KonkyWonky

The TV program Mythbusters did a program on this although I can't remember the outcome. It may be on YouTube or something but I would imagine it will depend on your model of car and age, like everything else as things are around longer they get better at designing them and they become more efficient.

Armengar

engine type may be a factor. Torquey diesels may be more efficient at driving the AC compressor over a petrol model. Also if you dont run your aircon then it wont get lubricated resulting in cracked pipes and bigger bills.

sarah_elton

Kingsd316 wrote: »

I pretty much have my air con on every time im in the car, even in the winter, (as air con is not just for cooling the car) and ive not noticed any massive affect on fuel

Last year, driving home from the Lake District (306 miles; 290 of which were motorway), OH and I had air con on the whole way. We used a smidge over a tank (stuck a tenner's worth in at the rip-off motorway services as we realised we wouldn't quite get home on the tank).

This year (last week), we didn't use the air con at all on the way home. We did it using just under 3/4 of a tank (same car).

So my car uses very roughly a third more fuel with the air con on (traffic jams etc were comparable to last year's run, as was my speed when we were clear of jams ).

EDIT: reading the replies above, a/c shouldn't have increased my consumption that much, maybe my car was just leaking petrol last year or something.