Does air con really eat your fuel?

SusieWinwood

Further to my thread the other week, we are almost certainly buying a Nissan Note 1.6SE Automatic this week.

It comes with air con and I asked the sales chap does it really eat fuel? He said well if it does say 30mpg without it on, if you put it on it might do 29. It's this just salesman talk or does it really not use a lot?

TIA

Susie

harveybobbles

Yes it does, but it's hardly noticeable, but to be honest if you drive with the windows and/or sunroof open it will have the same drag effect and reduce the MPG anyway...

One for MythBusters, perhaps...?

alleycat`

From the AA (doesn't say how they got the figure)

"The impact of using air con can pump up fuel consumption by up to 11% on slower roads."

I think up to a certain speed having the windows open is more economical (in drag terms) and over a certain speed aircon is more economical (with the windows closed) IYSWIM.

Both obviously cost you fuel in terms of either drag or power draw.

moonrakerz

alleycat` wrote: »

"The impact of using air con can pump up fuel consumption by up to 11% on slower roads."

This figure carries as much veracity as:- "up to 8mbps" !

I have a 1.6 petrol engined Ford, I do not notice ANY difference in fuel consumption.

iolanthe07

Though I accept that it must logically increase fuel consumption, I have noticed no difference at all, so it is marginal - nothing like 11% in my case, anyway. The comfort of having air conditioning, and its demisting properties in the winter, far outweigh the cost, imho. Don't forget to run it regularly to keep the seals from drying out.

alleycat`

I didn't say i agreed with the AA figure.
It was just something i found to quote for the OP.

I know with the A/C on my Touran loses about 1 to 2mpg on a long run (so hardly the end of the world) but it is noticeable.

I just open the windows on lower speed roads.

I would also suspect the condition of the compressor would have an impact as well but again i have no evidence to back that up other than the logic that more power draw has to come from something.

SusieWinwood

Thanks for your replies.

We probably won't use it a lot anyway as I do like my window open lol!

Perhaps do a test run see what its mpg is with it on and off.

Cheers

Susie

Strider590

It I think depends on whether the aircon is driven from the auxiliaries belt or not, if it's fully electric....

Like for example EPAS (Electronic Power Assisted Steering) which uses an electric motor instead of the belt driven hydraulic pump system used in old school PAS.

Anything extra that the engine has to physically move, will always have an effect on fuel consumption... Electrically driven devices have very little negative effect.

Vomityspice

harveybobbles wrote: »

Yes it does, but it's hardly noticeable, but to be honest if you drive with the windows and/or sunroof open it will have the same drag effect and reduce the MPG anyway...

One for MythBusters, perhaps...?

They have done this myth already.....twice!

See: http://mythbustersresults.com/episode22

Indout96

windows and/or sunroof open

Roof down on mine drops MPG from around 33mpg to 27mpg but its worth it LOL

missile

According to Mythbusters

Going less than 50mph it is more efficient to leave your windows down, but going greater than 50mph it is more efficient to use your A/C.