Does Cruise Control Effect Fuel Consumption?

wildnomad

Member
This seems subject to debate. Was wondering if anyone out there could shed some light on this matter.

...As an after thought - Does anyone know how many MPG gets knocked off using the Climate Control?

I have a 1.6 FSI :)
 
Mine seems to be better as it keeps everything steady.
My right foot requires constant concentration so I let the cruise take up the strain.
I try not to use the climate at all as it does sap 2-3 mpg so I thought
 
But if you don't use the aircon to save MPG but instead open the windows, then that's actually worse ;)
 
Well, as I always tell people who have me install cruise for them, it all depends on how you drive in the first place:

If you're already a very careful and diligent user of the right pedal, then it's unlikely that cruise control will improve your fuel figures. However, if you use the accelerator more like a switch, and you tend to creep up above the legal limits on motorways, then cruise will certainly help to get more miles from a gallon.

As to how much of an effect climate has on consumption, it's anywhere between 4 and 10%, but put it this way, having a window open will hit you harder.

Cheers,

Mike
 
I've also heard it said that on the flat, cruise control is pretty good from a fuel consumption viewpoint, but in hilly country it is costs quite a lot of MPG (because it's powering up the hills). Driving manually you'd normally lose a little speed on the uphill, and that's better.
 
a petrol will increase consumption because the petrol injection won't be turned off on the way down hills, leading to minimal increases. for diesels? I think it's 0, but I would have to check.
Other than that? Powering up the hill is the most efficient way of doing it.

Bret
 
Thanks everyone!

I was also wondering how it maintains a constant speed on a steep down hill without using the brakes or changing gear? Or does it use the brakes?
 
The cruse control dose not use the brakes, so it can pick up speed on down hill runs. You have to watch out as they seem to like putting speed cameras at the bottom of long hills.

Cheers

David
 
Based on experience, it keeps getting better because I am driving on steady speed and no sudden acceleration or stepping on the gas pedals. Though not really based on any concrete results or observations, climate control seems to be sipping up heavily on fuel that is why I try to stay away from it. I guess that you should just use it when you feel the heavy intent to use it, but not for something auxiliary.
 
Just a thought on open windows, I know its all subjective but do you think an open window with climair/heko deflectors would cause more or less drag than without. (Anyone got a wind tunnel to play with??) Clearly an open window without would use power but then what about when you crack open a rear one to get rid of the helecopter effect? which is caused by the build up of internal pressure? (Think I am prob the saddest person on here if I ponder on such matters) Cheers Colin.
 
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I don't have a scientific answer, but consider this, all efficient cars have smooth bodies so opening windows must have negative effect on MPG. Also, I was told hardcore track cars like 911 GT3 have air con because opening windows will create drag to slow it down more than the effect of added weight and drain on the engine! I'd say opening the rear windows will make it even worse as the air can make a long route by entering from the front window and exit at the back.
 
I think it's dependant upon speed - if you're going over 40mph then climate control is better than having the windows open, whereas if you're going slower than 30 opening the windows is best. Of course, if you turn off the compressor ('econ') & turn up the fan, that's better than running the climate control in any case.
 
A flow has less drag than a dead end, so at a guess opening the front & rear window is probably more fuel efficient than just opening the front. Plus your ears are saved from the pressure waves...
 
My experience with the AC is that, when it's first switched on, the consumption increases by about 10mpg but after the temperature in the car has come down the increase drops to about 4mpg. I mentioned this to a guy who was doing a re-gas for me for me and he said that it may have a variable compressor although he didn't know for sure.

Out of interest at 8 years old and 90k miles the system was still sealed and the re-gas was not required.

I used the instant read out on the computer on a flat bit of motorway with the cruise on at 60mph to get the figures above.

Overall town and motorway I get 55mpg. The car was re-mapped by AMD in the early days and gives 112bhp. I belive it was the first 90bhp car they did.

I sometimes think of having the re-map done again as I'm not that happy with the consumption. The earlier re-map was done by the previous owner who is a pal.

Cheers!
 
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