Air con knocked 10mpg off my economy!

[TheRobinK]

One of the biggest "boosts" I've ever had to fuel economy was driving on the M6 in England, in heavy traffic. 

 

I was either surrounded by lorries or following other cars by no more than a car length (no safe distance possible - leave a gap and someone is in it in seconds). MPG was up by about 6mpg more than I had seen before or since - I put it down to(involuntary) slip-streaming...

[jafo]

I have tried to see what affects the fuel consumption but I wasn't able to make any connections between fuel consumption and different factors - weight, speed etc...

Fuel quality will also have big impact on the consumption.

[Greenline3Matt]

Out of interest I tracked my mpg on my commute today, air conditioning on, I was down around 8mpg on normal. It does seem to have quite a hit. I'd rather be nice and cool though, especially when it's as hot as today!

[bigjohn]

It does seem to have quite a hit. I'd rather be nice and cool though, especially when it's as hot as today!

 

I would have gladly onl done 20mpg today for air con - lovely an cool driving home. Problem is you have to get out of the car eventually.

 

Despite air con being on going to and from work my economy didn't seem that different to my average. I filled up this weekend and after about 100 miles of some town driving and my commute showing an average of 45.9 (suprisingly maxidot nearly spot on this car/engine compared to measuring tank-tank).

 

My manual aircon was on both ways but trip mpg was better going to work (53)  than coming back (45) - It was much hotter coming back though (32deg C).

Edited 19 July, 2016 by bigjohn

[andrehj]

By the way, there was quite hot outside like a month ago. I drove home when it was 32-34 degrees outside and my air con worked rather hard. Fuel consumption was like ~4,3 l/100km - no more than average.

That can easily be explained: The extra fuel consumption of the aircon was compensated by the lower drag, caused by the thinner air (due to the high temperature).

[nazitf]

 Does the the compressor fully turn off when air con turned off?

 

I’d also like to know the answer to this. Often I’ve had a higher outside temperature than what has been selected on the climate control. With the AC switched off, I still get slightly cooled air entering the cabin, certainly not as cold as when the AC is on but it did make me wonder whether the AC system is ever completely turned off?

[peterposh]

Isn't it  an electric clutch on the pulley which engages when the air con is activated?  So when it's off the pulley just rotates with the belt without the compressor turning ( that's how it is on the mondeo anyway)

[bigjohn]

Isn't it  an electric clutch on the pulley which engages when the air con is activated?  So when it's off the pulley just rotates with the belt without the compressor turning ( that's how it is on the mondeo anyway)

 

No, the last Superb that had a compressor clutch was the MK I

 

Most use clutchless variable displacement compressors these days

Edited 29 July, 2016 by bigjohn

[peterposh]

That was on my MK3 mondeo mind, , I can't see the a/c pump  on my mk4 ( and I don't want to either as that usually means trouble)

 

 

 

https://axleaddict.com/auto-repair/Variable-Displacement-Compressors  

Edited 31 July, 2016 by peterposh

[vkd]

I do 440 miles round trip every week on M6 and M74 and manage to get between 45 to 50 mpg on my DSG 170 BHP Elegance and didn't noticed a lot of difference (surely not 10 mpg) with or without aircon. As said in other comments there must be other variables contributing to that big a difference.

[g_tee]

Lol at "only managed 56" - best I've had is 38mpg and I love it