How much extra fuel does the climate control take when in cooling mode. What the miles per gallon do you peps get when running air con.

do a few searches, been discussed many times before. Leave it in auto all year round. Trouble free, and there's hardly any additional fuel usage. In summer when the compressor is running more often than not then sure it uses a little, but not that you'd notice. More fuel is used if you open a window or a sunroof. Vipes

Hi, I must agree with the above. Yes AirCon will put an additional strain/load on the engine but less than that of opening the window!!! Windows open increase fuel useage by about 10%!!! Ouch.. Des. . . ;)

I have my climate on all the time. I've switched it off a few times to see if consumption improved and noticed no discernable difference. As stated, leaving a window open or carrying roof boxes will use far more. Also depends on how you drive the car. If you tend to "toe it" a lot I would expect this to magnify any drop in consumption with the climate on. Best consumption would be achieved with no aircon, no other electrical items on and frugal use of the right foot, so you be cold, bored and late and couldn't drive at night!

I was just wondering why running electrical items lowers fuel consumption, ie headlights. Considering the alternator supplies the charge and would it apply to a diesel which doesn not use a spark, because I can see the quality of spark might be affected. Even though I have read having headlights on increase fuel consumption by 3% I have never read the reason why it happens.

Knock yourself out at: Just tell the wife where you're going before hand. You might not surface until the New Year and I guarantee you won't just stop at alternators.

Lights-on means slightly more current drain from battery, which in turn means slightly more load on alternator to keep battery charged, which in turn means slightly more load on engine as it turns alternator via pully... hence slightly more fuel used. Saloon racing/rally cars sometimes use a device that stops the alternator charging the battery at full throttle (used to be marketed as 'Alterpower', driven by manifold pressure sensor) to save the loss of a few bhp.

Hi. Enlighten me a little. My V70 has a switch for the "auto mode" and seperate switch for the "air-con mode" Assuming the "auto mode" is on, is there any difference to switching the "air-con" switch on or off.

If you select AUTO then turn the air-con off - then the fan speed / temperature will still be automatic, but without the air-con running. (If it's like the S60 - but it sounds a similar sett-up) This time of year though the air-con is obviously not used for cooling the car down - but for dehumidfying the air. It will only run when needed. You really should use the Air-con for a good 15 mins concurrent a week ( and by that I mean it actually cooling - ie turn the temp right down) if you decide to turn it off. If you don't use it, then you'll be looking are more frequent re-gassing, and also potential leaks. When you first turn it off, you may find the windows mist up, this will soon past after a couple of days, just have the window open a smidge in the meantime. The air-con does obviously use fuel, as stated previously due to the extra load - but the amount it uses is nothing compared to the costs for regassing / maintenance etc. Vipes