General Aircon and MPG

[Matthen]

Morning all,

I'm curious to know what effect having the A/C Compressor running has on your MPG.

Previously I've been getting 31/32ish MPG around town (nasty short journeys, need the car for the load space). This is about what I expect, there are an awful lot of speed bumps and traffic lights around here.

I've had the A/C on pretty much since filling up, and Yesterday I flicked over to the OBC and was rather depressed to discover the figure 28.2 MPG over the last 21 miles - the needle agrees with this, it's just starting to move off full.

This equates to a 15% increase in fuel consumption - does this correlate to your experience?


Car is a 2008 TJet 150.

 

[aurick86]

In hotter weather you can expect closer to 20-25 increase in consumption.
The AC does require a lot of power to run, there is no way around it.
Maybe having wind deflectors installed.. so you can leave the windows 1cm opened can help a bit (no more fear of rain)

The consumption will be dramatically bigger if you only do short journeys:
Just imagine.. car sitting out in the sun.. then you get in it and start it.. cold engine.... the car will need to burn a lot more petrol.

 

[Cadabena]

We've been making use of the remote electric window feature lately, so the car isn't quite so Mordor-like when getting in. Quick press of unlock, hold unlock to move all 4 windows down a tad, relock - all from inside the house. It's the little things

But then we still can't resist the climate control once moving. However since mother nature's done the difficult bit, the compressor doesn't have to work nearly as hard - from my (hardly) scientific testing, fuel consumption doesn't really seem to be affected.

 

[glenn2602]

My old Mercedes 2.8 used to drop 4-5mpg when the air conditioner was used. That's a 25% drop in mpg..

My 900cc Cinquecento doesn't have any ac.. just wind up windows that rattle a bit ..

I never use ac in my 4 litre jeep.

Oh yes, ac affects your mpg..

 

[Matthen]

Yes, it does seem to.

This is the first petrol car i've had - with the diesel I had before it was not as noticeable, I guess I just wasn't expecting a figure that low to appear.

I've also noticed this week how much more fuel cruise control seems to use - Easily cracked 40 MPG using my right foot this week, rather than the 36.7 the cruise usually returns.

This is especially surprising as I was driving faster than I do usually.

 

[Cadabena]

Yes, it does seem to.

This is the first petrol car i've had - with the diesel I had before it was not as noticeable, I guess I just wasn't expecting a figure that low to appear.

I've also noticed this week how much more fuel cruise control seems to use - Easily cracked 40 MPG using my right foot this week, rather than the 36.7 the cruise usually returns.

This is especially surprising as I was driving faster than I do usually.

What engine do you have? Our 120 Tjet did Birmingham to Devon the other week, probably 80:20 motorway:A-roads, trip meter reset door to door and got:

Going there: cruise control, ~85-90mph, climate on, 38mpg
Coming back: cruise all the way, ~65-70mph, climate off, 46mpg

It was as we came off the motorway it reached 46mpg, so was obviously doing more on the motorway.

I think the cruise might use more on A roads or when there's big elevation changes (it seems to decide to kick in very quickly), but on a level motorway it doesn't seem any worse than my right foot... although that could be saying something about me :devil:

 

[dtwelve]

theres a programme on TV called myth busters and they did a car with windows opened and car with a \c on and it was the same mpg for each