What air con does to your mpg

real1314

A comparison of using aircon or windows:

"Test #4 A/C On, Windows Up vs. A/C Off, Windows Down

This has got to take you back to the days with the family on vacation. Dad says, "Turn the A/C off! It wastes gas!" And Mom says, "We can't roll the windows down or everyone on the highway will think we can't afford A/C." And you're in the back roasting, hoping someone will win the argument so you can cool off.

Well, family psychology aside, if dads are still saying this, they aren't necessarily right. While the A/C compressor does pull power from the engine wasting some gas, the effect appears to be fairly minimal in modern cars. And putting the windows down tends to increase drag on most cars, canceling out any measurable gain from turning the A/C off. But this one depends on the model you're driving. When we opened the sunroof in our SUV, the mileage did decrease even with the A/C off. Still, in our experience, it's not worth the argument because you won't save a lot of gas either way. So just do what's comfortable.

Method: We drove the full 55 mile-loop in two cars at equal speeds both times — 65 mph. The first loop we drove with the A/C on and the windows up. The second loop we drove with the A/C off and windows down. In the second test we drove 20-mile loops. This was far enough to see our gas mileage level off and remain steady on the computer trip meter."



Ok, depends on the vehicle you've got, but then the drag probably changes with vehicle too (that Zafira with 4 windows open will be worse than a supermini, given that the internal volume of the vacuum is greater).

More fueld econmy tests here: http://www.edmunds.com/advice/fueleconomy/articles/106842/article.html

multimillionaire

Turning AC / Climate Control totally off can be problematic if rarely used and leave you with an expensive repair bill. The components conk out through lack of use.

This also explains the seriously nasty damp smell you get when you switch back on after having been off for a while.

Best to leave it on, be it at a matching temp as outside with the fans off when not actively being used.....

Just my 2 pence worth!

MM

Murphy_The_Cat

multimillionaire wrote:

Turning AC / Climate Control totally off can be problematic if rarely used and leave you with an expensive repair bill. The components conk out through lack of use.

This also explains the seriously nasty damp smell you get when you switch back on after having been off for a while.

Best to leave it on, be it at a matching temp as outside with the fans off when not actively being used.....

Just my 2 pence worth!

MM

that was me t'other year. I saved £20 in diesel by not using the aircon during the Winter and got a £80 bill for cleaning out the system and recharging it !

MTC