MPG with C/Control on

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oorjim2

Active Member
Joined
Aug 7, 2008
Messages
149
Location
Motherwell, Scotland
Car
03 CLK 320, 09 Corsa 1.2
Hi
I always thought that using cruise control on a long drive would give you better mpg. Was down in Lockerbie today for lunch and used the c/c but only got 30.2 mpg, yet a couple of months ago coming up from Liverpool and not using the c/c I got 36 mpg, both times average speed was 80 mph.

Jim.
 
Yes I think this is a common misunderstanding - I too have found CC uses more fuel so I no longer use it..

I also prefer Speedtronic....
 
Shouldn't be that big a differnce. The main difference I notice with CC on the the way the car pulls (pushes) itself around the bends at 80mph and how much the other traffic slows. Ok it's probably only 2mph difference, but if it's quite busy I often find myself having to disenge CC on the bends to avoid crusing into the cars in front. This keeness to maintain the exact speed probably looses a fraction of an mpg, but >5mpg seems extreme.
 
I know the car is due a B service in about 4000 miles maybe that has something to do with the mpg not being as good as it was.

Jim.
 
I love the cruise control and always use it on motorways - which is not very often as most of my miles are tootling around London.. I can imagine it is not the most economical way to maintain speed as it will kickdown a gear or two if you engage it after slowing to say 40-50mph due to traffic congestion.. quite good fun though.

Ade
 
As with all tools, it depends on how you use it. No doubt f you use it in ways that cause a lot of unnecessary acceleration followed immediately by braking, that's not going to be very good for fuel economy, but is that the CC's fault or the driver's fault for abusing it?

I'm going to go against the fold here and say that in my long experience with cruise control, fuel economy is better in proper CC circumstances (i.e. long stretches of motorway at pretty stable speeds).

Of course, the above is just my opinion. You read all kinds of opinions on this, but as often the problem is that little of this is backed up by solid data. A bit of googling though brings up a lot of anecdotal evidence that CC on motorways makes for better fuel economy and so confirms my personal experience.

I'd be interested to hear if anyone has actually objective data on this from a credible source.
 
I can imagine it is not the most economical way to maintain speed as it will kickdown a gear or two if you engage it after slowing to say 40-50mph due to traffic congestion.. quite good fun though.

Ade

I noticed this for the first time today, actually. Cruise was set dead on 70mph and i'd disengaged it and dropped to about 40 in a 50 zone. When out of that zone, i pulled the lever and after the 2 second pause, the car dropped two gears and went full throttle to 80. Normally it just wafts there, was quite funny :)
 
I'm going to go against the fold here and say that in my long experience with cruise control, fuel economy is better in proper CC circumstances (i.e. long stretches of motorway at pretty stable speeds).

Of course, the above is just my opinion. You read all kinds of opinions on this, but as often the problem is that little of this is backed up by solid data. A bit of googling though brings up a lot of anecdotal evidence that CC on motorways makes for better fuel economy and so confirms my personal experience.

I'd be interested to hear if anyone has actually objective data on this from a credible source.

I'm going to agree with you here, I do find that on long 200 mile + runs I do get much better MPG with the cruise on. I can't accredit this with fuel quantities etc, but lets just say i get much more out of a tank of fuel than I do on my usual 100 mile a day motorway commute.

When driving the auto box normally with no cruise on, i 'throttle back' as much as I can without any loss in maintaning speed. If i then engage cruise, then i do see that the revs may drop by as much as 50-100 rpm again on the rev counter, and it does seem to stay like that for most of the way.

My daily commute is on quite a up and down hilly part of the M4 and even when going up steep hills I don't notice that the car ups the revs anymore - here I guess momentum is playing it's part and the car (unlike me) is less likely to overcompensate with the throttle.
 
I noticed this for the first time today, actually. Cruise was set dead on 70mph and i'd disengaged it and dropped to about 40 in a 50 zone. When out of that zone, i pulled the lever and after the 2 second pause, the car dropped two gears and went full throttle to 80. Normally it just wafts there, was quite funny :)
Has been discussed before that the speed at which the car resumes reflects the speed at which you reached the original crusing speed i.e. the the adaptive throttle was in sporty mode, when you set the cc that's the mode it resumes in.
 
My personal experience tells me that cruise control will kill your MPG figures.
Feel the way the car will accelerate uphill to keep the same speed with CC engaged & then without CC on, see how far you have to press the accelerator to get the same response to give you an idea how much fuel you are wasting.

Also, when cruising on the motorway, after reaching say 70mph, you can release the pressure on the accelerator about half an inch without the car slowing down, thus saving fuel. Cruise control will not do this.

Russ
 
Spent much off my life doing 30-40k miles a year and have done extensive tests with cruise. Properly used it saves fuel. That is to say when used on fairly clear motorways/trunk roads so that you are not continually putting it off and on. If the speed keeps dropping cruise is designed to return you briskly to that cruising speed.


Instead of resuming cruise when the speed has dropped 10 or 20 miles per hour (in which case it will accelerate briskly to the chosen cruising speed -which is not good for economy) all you need to do is accelerate gently yourself to regain cruising speed economically and then resume the cruise control.

We do 3,000 miles each year in France during a two week holiday and cruise is a godsend on their half empty motorways and by keeping to a steady speed is more economical than the average driver whose speed does vary quite considerably.
 
IMHO

Super gentle right foot MPG < Cruise Control MPG < Normal right foot MPG
 
I have used it quite a lot in the past more to stop me from speeding as I do tend to have a heavy right foot. This is the first time I have checked the mpg and was expecting it to be better. The M74 was not all that busy and there was only roadwork’s for about 2 miles. I suppose its better getting a couple of mpg less than points and a fine.

Jim.
 
IMHO

Super gentle right foot MPG < Cruise Control MPG < Normal right foot MPG
I think you mean > rather than < so that your super gentle right foot does more mpg than cruise IYO.

IMO if you use the super gentle right foot to get up to cruising speed then set cruise for a constant speed it cannot be different from a driver holding the same constant speed. It is accelerating and decelerating that spoils the mpg figures.
 
It is accelerating and decelerating that spoils the mpg figures.

I have a suspicion that one of the reasons that CC doesn't work for some drivers is that they normally disengage it by braking.
 
I think you mean > rather than < so that your super gentle right foot does more mpg than cruise IYO.

Spot on!!

IMO if you use the super gentle right foot to get up to cruising speed then set cruise for a constant speed it cannot be different from a driver holding the same constant speed. It is accelerating and decelerating that spoils the mpg figures.

The reason I think a super gentle right foot tends to yield a slightly better result is that I can anticpate crests and dips and moderate the throttle slightly earlier than the CC can.

I suspect that makes more of a difference on A roads and dual carriageways than motorways though.
 
I had a Mondeo 2.0 auto 15MPG(YES 15MPG) urban.Used lots of CC on motorway and got 22MPG.Usually my MPG improves by 30-50% on motorway - but not this time - was probably better off not using it
CC is supposed , in theory to improve MPG
 
I think you mean > rather than < so that your super gentle right foot does more mpg than cruise IYO.

IMO if you use the super gentle right foot to get up to cruising speed then set cruise for a constant speed it cannot be different from a driver holding the same constant speed. It is accelerating and decelerating that spoils the mpg figures.
:)Hi,

I agree with hawk20 here - it is possible using the lightest of pressure and the contours of the road to gradually build up your mpg,using cc to achieve that is not as effective,however,once you have maxed out on your mpg,engage the cc and it will sit pretty constant - anyone agree ?

Alex
 
Sit at 65mph with CC on & you will be shocked at the difference!
 

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