car air con

[RegandPat]

My first car with air con that works, great, and with this heat I have it going full blast and some times open a window just for some fresh air for the dog in the back.
Then my daughter tells me you use more fuel with air con running.
Well I suppose a little fuel, can some one tell me how much?
Like 1 to 10, 10 being don't use it ever and 1 don't make any differants.

Reg

 

[John_374564913]

There are a number of factors involved it would and does depend on the age of the car because modern day cars the amount of fuel used having air con is negligable which was not the case for erly cars when air con was first introduced.

Another factor is what setting you have the air con on as fuel is consumed when the compressor is engaged so if you have the air con set to low then the compressor is fighting to keep the vehicle cool and to do that it is engaged and working which causes resistance and ups the fuel consumption.

sorry I can't be more clear than that but not knowing the age of the car it is difficult to say
i think the bottom line is with any car fuel consumption will be increased with a compressor working.

John

 

[william_5128769]

You will use more fuel but possibly not a lot. I have found on my car it will drop by approx 2mpg but I am happy with this if it keeps me cool. I have also read in motoring mags that running with the windows open uses more fuel than air con and windows closed. What you don't want to do is have the air con on and windows open as you are then getting the worst fuel consumption while trying to cool the great outdoors.

 

[RegandPat]

Thanks John for the reply, the car is an old P reg audi automatic 1800, I say old but it is new to me, go's like the wind down hill.
The setting is set to Lo or some times Pat go's up to 18, I must admit you can hear like a compresser sound from under the bonnet.

 

[hgv dave]

Hi all
Believe it or not you will use more fuel with the windows open than you would using the aircon.
It's because with the windows open the car is less aerodynamic and uses more fuel

Hgv dave

 

[colin-yorkshire1]

and dont forget to use it regulary as they stop working if not used and cost a fortune to be mended, the AC did not work in the mondeo when I bought it cost for repair £160 so it stayed broke,

 

[ProfJohnL]

Helolo Reg and Pat
The bottom line is that using AC will add aditional load to the cars engine, and use fuel. In older cars the AC was either on or off where as more recent cars may have climate control which turns the AC on or off according to the actual temperature in the car. The latter is more economical.

I belive that a typical AC compressor in a car will use between 5 and 10Hp of engine power so in some cars you may actually feel the compresor kick in/drop out

For best and most efficeient effect the windows need to be kept closed. The car will have enough fixed ventilation to ensure the occupants do get enough fresh air.

 

[ChrisUK]

It will use a little more fuel, but its worth it. On a long journey at fairly constant speed I tried with and without and monitored the cars mpg computer. I could see no difference. Not very scientific but a guide. It is important to use the ac at least once a week, even in the winter to keep the ac seals ok. Remember the ac also dries the air so demisting is much better.

 

[Cruzer]

Mythbusters did an episode on this and concluded that (in general) it's more fuel efficient to open the windows than run the air con, up to around 50 mph. Faster than that close the windows and put the aircon on.

I wouldn't worry if you're doing it while towing. I suspect the van make a bigger dent in the consumption than air con.

 

[Steve L]

Air con makes vary little difference to fuel consumption and as already suggested running it frequently does pay dividends.
My Brother-in-Law has an S type Jag which due to his working away from home only get's used at weekends. He went to France on holiday last year and that was a nightmare. On the way down the aircon compressor siezed from lack of use. He had to use two hire cars while on holiday in france, then do a walking passenger transfer with all the luggage and two kids to get back to uk, hire a car at the ferry port to get home and then a week after his holiday nightmare he had to ring me at 4am as the taxi had not shown up to take him 60 miles to Birmingham airport. Then he flew to Lyon, taxi to the garage, drive car after paying 2200 euro's for the repair, to Calais. While he was on route we booked him a ferry ticket to coincide with his arrival at Calais (£98 one way). Then he drove 350 miles to Leominster. All told he was up for 30 hours straight and with rentals hotel rooms etc, he was about £3500 out of pocket.

He has now taught his OH who can't drive, to start the car switch aircon on and run for 10 mins every other day. It's cheaper than the repair bill for the next three years!!!!!!!!
As my Rover has a simlar compressor you can guess what I do. And I still get upto 64 Mpg solo and 37Mpg towing when we move sites twice annually at present.