MPG with C/Control on

[whitenemesis]

Cruise set at 70mph =

 

[BTB 500]

Also cruise control set at 70 mph:

with a caravan on the back

 

[whitenemesis]

BTB 500 - ouch!

Nice example of both ends of the spectrum though

 

[Ted]

Cruise set at 70mph =

WOW! that is seriously impressive!

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.

Jim.

I find the speedtronic better for that.

 

[Wezzel]

I did two similar 300 mile trips to the Lake District from Surrey, both in the early hours with clear dry motorways. On one trip I used cruise and got mid 40's mpg the other I completed without cruise and achieved a fraction over 50 mpg. Both trips were driven at a steady 70mph.

I think where the economy loses out is on the hills. Without cruise it is human nature to speed up slightly going down hill and then back off the accelerator a little and use that momentum to give you a slight headstart going back up again, slightly tailing off speed on the way up. If cruise maintains the exact speed it has to accelerate harder on the up portion of the hill.

The thing to do would probably be to use it on the flat sections but click it off on the steeper hills.

Just my two penneth

 

[flango]

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.

A bit of objective data for you, well I think it is. When I worked for a company managing their Scottish operations I used to travel the same 500 mile journey each week there and back from Doncaster in South Yorkshire to Ayr in Scotland taking the following route A1- A66 -M6 - A74 -M74 - A70 approx 80% of this route is motorway or dual carriageway and the times I used to travel it, it was fairly empty so a good case for using cruise control. The last car I did it in was a C180 Kompressor using cruise control gave an average of 34mpg without gave an average of 37 mpg some 9% better, I tried this on numerous occasions over the years and the fuel consumption was always better when you did not use cruise control. This also applied to the following cars which were also used over the years BMW 318i, Volvo V70 T5, Seat Leon Cupra 150 bhp Diesel, Subaru Outback 3.0R. I have never driven a car yet that is better on fuel when using cruise control and hence have now stopped ordering it when I order a new car. Just my experience but IMHO cruise control costs you money not only in extra fuel but also in paying for it in the first place as an option

 

[glojo]

If you get a better return using cruise control then you need to look at your driving style.

Cruise Control is a nice luxury feature that takes the strain out of the journey It is NOT a computerised radar that is capable of either thought or anticipation. It has NO idea of any potential hazard, hills or obstructions.

The easy comparison we tend to offer is this but the doubters will say the cruise control was switched off too quickly. I will suggest that if it were left on any longer then the journey would not have been completed.

You are driving along a trunk road and see a slight hill in front of us, we have a number of options. We can allow the car to loose a few miles an hour because we know that on the other side of this slight hill is an equal downhill stretch where we can retrieve those lost 'miles'. Cruise control will keep the speed at the set figure, increasing the throttle and then on the other down hill stretch it will slow the car to keep it at the set speed.

I am a big fan of cruise control and my wife will always use it on our motorway journeys but it is not an all thinking, all calculating drivers aid.

Regards
John

 

[Mactech]

I think that about sums it up John!

Love or hate Clarkson you my well like this:

http://uk.youtube.com/watch?v=DMuO-8S_0Wg

 

[glojo]

Love or hate Clarkson you my well like this:

http://uk.youtube.com/watch?v=DMuO-8S_0Wg

Mega ouch (it really hurts when I laugh)

Thanks for the pain

Regards
John

 

[Roger Jones]

"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)."

I agree. I've used CC since 1989 on my own cars and prior to that in US hire cars. I have a gentle right foot, but it's not as good as the CC system. There is hard evidence of this on the Web somewhere in the form of a graph -- wish I could find it again. I know from occasional experiments that it helps me get 27+ out of my W124 E320 Coupé. I use it most of the time, flicking it on and off when necessary -- so easy to do with that well designed VDO stalk. I do find it helpful as a relaxing factor on long journeys.

It will increase fuel consumption in hilly areas.

Most if not all of the fuel-saving tips sites suggest that it be used.

http://tinyurl.com/4q3t9z

http://tinyurl.com/jtd4a

http://tinyurl.com/446quj

[P.S. "Caravan on the back at 70". Please let me know when your next towing trip is due so that I can stay indoors.]

 

[Mudster]

Mega ouch (it really hurts when I laugh)

Thanks for the pain

Regards
John

You'll like the original then...Python's Whicker Island..

http://uk.youtube.com/watch?v=Cn8Pua5rhj4

 

[Mactech]

I'm glad it says 'General Discussion' at the start of this as I don't think it has a yes or no answer.
The problem starts with everone's driving style being different. In the same way that some will not achieve the manufactuers fuel consumption figures and even less will exceed them.
So cruise control on is more ecomnomical than what?
Having observed the driving of many on our roads then I would agree that using cruise to maintain a good constant speed could bring benefits to the majority drivers.
However, for ultimate economy the careful control of the throttle setting by the operator who has the advantages of anticipation, observation, feel and is paying attention will always give a better result.

 

[Dieter]

Hi,

I use c/control ALL the time and, frankly, couldn't care a less whether it's more or less fuel efficient than my right foot.

All I know is that I get better mpg in my ML than in many of my previous cars (not SUVs) which never had c/control....so it does for me.

I have never really understood why people with 'expensive' cars worry about an extra/less mpg or two.

Cheers,

 

[st4]

I also think CC detracts from ones concentration and takes a vital part of the car control process away, and by being locked into a specific speed you can find yourself in siutations you wouldn't normally have been in if you had:

A) gently accelerated to drive out of the hazardous situation
B) gently slowed down to avoid getting into the hazardous situation - just because a road is long and straight and has a 70 limit doesn't mean its without hazards

I find my MPG is significantly better without CC and I wouldn't know what to do with my right leg if it wasn't operating the right or middle pedal. If people find they use CC for driving comfort then I reckon its because they aren't sat properly in their car.

Even if CC was better on fuel, I still would't use it as I like to control my car. I drive it, it doesn't drive me.

 

[Mactech]

My wife dosn't understand me either....

She dosn't understsand why people want to climb Everest or set landspeed records....

 

[BTB 500]

Both trips were driven at a steady 70mph.

If you mimicked CC exactly (maintaining dead on 70 all the time) then the fuel consumption would be the same. As mentioned, the point is that most people don't - they slow down going up hills and round even the slightest bends. So not really comparing like for like.

 

[flango]

I also think CC detracts from ones concentration and takes a vital part of the car control process away, and by being locked into a specific speed you can find yourself in siutations you wouldn't normally have been in if you had:

A) gently accelerated to drive out of the hazardous situation
B) gently slowed down to avoid getting into the hazardous situation - just because a road is long and straight and has a 70 limit doesn't mean its without hazards

I find my MPG is significantly better without CC and I wouldn't know what to do with my right leg if it wasn't operating the right or middle pedal. If people find they use CC for driving comfort then I reckon its because they aren't sat properly in their car.





Even if CC was better on fuel, I still would't use it as I like to control my car. I drive it, it doesn't drive me.

Totally agree, particularly with your last point, thats also my reason for not having an auto, I want to tell it when to change gear not it to tell me

 

[BTB 500]

People used to have to manually advance/retard the timing too ...

 

[Wezzel]

If you mimicked CC exactly (maintaining dead on 70 all the time) then the fuel consumption would be the same. As mentioned, the point is that most people don't - they slow down going up hills and round even the slightest bends. So not really comparing like for like.

That's what I said in my post. I drove without cc at almost exactly 70mph but tended to very slightly speed up on the declines and let the speed drop slightly on the uphill. It's human nature. It would be near impossible to mimic cc completely and also a bit pointless doing so.

 

[whitenemesis]

I use CC so I can relax and cross my legs whilst doing the crossword.....

I must admit to never having considered the economy aspect of using CC. I use it because it's convenient to do so in the right situation.