# Topic for today. Is cruise control less economical?



## Zebedee (Oct 3, 2007)

I am interested by the differing opinions about fuel economy when using cruise control.

Some folk think it is less economical, while others (_me included :wink: _) are convinced that it returns a better mpg!

Two points to make clear for the sake of argument.

1) I have no fill-to-fill data - I have assumed that the dashboard meter will give an accurate _comparison _between CC on and CC off.

2) I'm only talking about motorway use, where there is little or no gear changing required.

What do you think?

I'm a pretty "gentle" driver, and am content to stay with the lorries when in the van an in "holiday mode", but I don't think I can get as good fuel economy as the CC under the same driving conditions.

Dave


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## HeatherChloe (Oct 18, 2009)

I tend to judge it by whether I have wasted fuel getting to a certain speed and then having to break - that's after years of cycling, where the main thing you want to do is not to break as then you wasted pedal power. 

What I have noticed is that when you go down a hill, the cruise control uses gentle engine breaking and not foot breaking and keeps it nice and steady at the same speed - so that seems to be to ensure that there is no waste. 

If I'm driving myself I tend to over do it - I often ease off the pedal too much and the speed then drops too much and I have to accelerate again - that doesn't seem as efficient.


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## Glandwr (Jun 12, 2006)

Got CC on van and car. I would say it is more economical on van and less so on car. How’s that for keeping the thread going Dave?

On the van (Sprinter 616) it is “gentle” ie if you fall below chosen speed it brings you back up slowly.

On the car (3 series BM) it is “performance” ie it gets you up to speed again with you being pushed back into the seat.

In short it depends on how it is set.

Dick


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## cabby (May 14, 2005)

It is cetainly easier on the foot and I would say more economical.

cabby


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## Hydrocell (Jan 29, 2011)

*Cruise Control*

Hi Zebedee

I too think that cruise control is a good fuel saver I always use it on motorways, and apart from giving a more relaxed dive it sure helps on the old feet and legs.
The parameters in the ECU are set to maximize fuel economy whilst using cruise control.
Every little helps?  
Regards
Ray


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## Rapide561 (Oct 1, 2005)

*Cruise control*

Less economical.

Russell


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## Crindle (Feb 2, 2007)

Hi all.......repeat my earlier posting on this subject and my view's remain the same:

"this is an interesting topic, particuarly the above excellent posting. AndroidGB brings together both negetive points in the use of cruise on UK roads. First I fully agree with his comment associated with crowded roads and the use cruise, just not comfortable for safe stress free driving IMO. Second locking the speed is always going to demand more fuel to maintain that speed over varying terrain.
Not sure about our current vehicle but on the previous American RV's all had Cruise Control (CC) using an extremely accurate form of feeding back the road speed to the engine control unit (ECU) which then operated the throttle or fuel control. They used an alternator made up of a permanent magnet on the drive shaft (rotor) spinning within stationery coils (stator). This delivered a current at a frequency depending on the speed of the drive shaft to the ECU. Deployment of CC at a selected speed delivered a reference frequency to the ECU. Any mis-match is countered by adjusting or feathering the throttle hence the speed to keep both frequencies in line. Such fine adjustments went unnoticed most of the time, just like being chauffeured by an expert driver. However as Android GB states only one parameter is being controlled albeit expertly it still remains against a fixed locked speed, and the necessary fuel to keep it there"

Hope this is of interest......Crindle.


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## Hydrocell (Jan 29, 2011)

If you have a led foot and keep pressing the acceleratory you mite be right Russ?


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## short-stick (Jul 23, 2007)

My observations...
Cruise control cannot "see" hills and thus cannot anticipate and drive correctly for the conditions. Build speed gradually before a climb, reduce power before the peak but with enough momentum to get over the top and reduce power on the downhill... All good driving techniques. If cruise control cannot see what is ahead, it is only reacting, not predicting. I've driven with and without cruise control and in my experience, I save more fuel without cruise control.


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## javea (Jun 8, 2007)

Comments from a Google search:

Earth easy - Fuel Efficient Driving:-

Use the cruise control. On long stretches of highway driving, cruise control can save fuel by helping your car maintain a steady speed.

The following comments were palgiarised from an Australian Yahoo site -

It saves you fuel no matter where you drive, for the simple reason that no person on the planet can maintain an exact speed as accurately as a cruise control. If you want proof, set it on 65 and drive down the flattest stretch of road you can find. You will be able to spot the people without cruise control because they will constantly be varying their speed, catching up to you, passing you, and falling behind you no matter how hard they try. If you disengage your cruise control, you will not be able to maintain a constant speed to within a half a mile an hour. A cruise control monitors your speed thousands and thousands of times a minute, and makes almost imperceptible changes to the throttle, giving the engine only the fuel it needs to maintain a speed. It does not get tired, it does not get fatigued, distracted, or fooled by hills or headwinds. In contrast, every time you slow down even a couple of miles an hour, it takes more fuel to return to your desired speed than it takes for the cruise control to precisely maintain it.

Personally, I use it on the long motorway stretches in France and Spain, reverting to manual throttle operation in the mountains. As I usually return 26.5mpg in a 3.85 tonne A class I think it works well. Also allows a much more relaxed, and therefore safer, drive.


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## WildThingsKev (Dec 29, 2009)

Use it a lot and I reckon it gives better mpg, BUT completely agree with Short-Stick that it fails on hills and I overide it for the steeper and/or sudden hills.


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## HeatherChloe (Oct 18, 2009)

I was thinking more about this, and realise that I don't care.

People ask me how many MPG my van does - I don't know!!! I wouldn't even know how to work it out - I buy diesel in litres not in gallons. 

I know that if you drive at 56mph instead of 70mph, you save fuel. But I don't do that (I did it when I was a broke student and 5 of us drove to Edinburgh and back - it took ages, but we travelled for £40 cheaper than the other car) . 

I didn't get my cruise control to save diesel - I got it to rest my foot and concentrate on steering.


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## Stanner (Aug 17, 2006)

Yes you may be able to get slightly better mpg if you don't use CC, but it takes a lot of concentration and can be a right pain in the ankle, knee and just about everywhere else.

It is really worth all that hassle for maybe 1 mpg at most if you are a truly expert economy driver?

Not only that all the speeding up and slowing down that comes from such "hypermiling" really really really p*****s off other drivers when you keep getting overtaken on every upgrade and then you creep past them again on the down hill bits (if they are long enough).

Use CC and just cancel it the right distance (I find 4-500m about right) before a roundabout so you coast in and don't need to brake (hopefully) - then hit resume as you exit the roundabout and gently accelerate back up to the set speed.

Having it fitted to an auto helps as well.

In my experience the people who can't get better _overall_ MPG using CC are the people who won't or can't learn how to use it properly.


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## SpeedyDux (Jul 13, 2007)

CC will cost me about 3 mpg worse versus non-CC driving unless the road is pretty much level. Building speed on a light throttle downhill, then letting the speed reduce gradually uphill will always beat CC for economy. If this annoys other drivers who I pass then who repass me if it's a 3 lane motorway just go a couple of miles ahead of me and you won't get bothered again. Mind you I see a lot of MHs going past doing 70+ so perhaps they don't much mind paying £1.40 per litre for diesel.

The only time CC is unbeatable is for sticking to the 50 mph speed limit in roadworks where they have SPECS average speed cameras.

SD


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## Techno100 (May 8, 2010)

It's just a damn sight more comfortable and if you want better economy you have to use your brain a little and combine every tool in the box. Of course you can't expect it to power you over a big hill, it's not designed to let you pop in the back and put the kettle on :lol:


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## Rosbotham (May 4, 2008)

javea said:


> It saves you fuel no matter where you drive, for the simple reason that no person on the planet can maintain an exact speed as accurately as a cruise control.


That presupposes that you want to maintain a constant speed...which on anything other than a dead flat road is the enemy of fuel economy. As others have said, it makes sense on downhill to ease off the throttle but let the speed build, and on uphill stretches to maintain constant throttle and let the speed drop (as far as is safe and the engine will let you do so without changing gear). Cruise control - however configured - will increase throttle on uphills to maintain the constant speed you've instructed it to do. That's bad for fuel consumption.

Similarly, unless you've got an expensive Jaguar system with integrated front sensors, cruise control won't ease off the gas when it sees traffic bunching ahead...it's reliant on you cancelling it to make that happen. Absent cruise control sensible drivers would ease off, with cruise control all too often it's wasting energy by braking.

I notice the google (I think) and Yahoo links are from countries where roads are straighter, quieter, and (on the whole) flatter. There, the loss of economy through using CC may well be offset by the gain through the vehicle not accelerating/deccelerating due to driver inability to hold a constant speed on the flat without it. Don't think that applies over here.

I use the CC quite a lot in my car with an auto box and big lazy engine. Doesn't suit the driving characteristics of my motorhome with a manual box and engine that's working harder.


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## Mrplodd (Mar 4, 2008)

Long flat section of road (like they have in the states) its more economical, hilly terrain (like the UK) it is less economical. because a CC doesnt know why the road speed has dropped so it will (usually) try to get you back up to the set speed ASAP. To do that it uses full throttle and that uses more fuel than a driver with a light foot who is happy for the speed to drop off on the hills and pick up slowly when on the flat again !

Simples

However CC DOES make for a much more relaxed journey !


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## Zebedee (Oct 3, 2007)

Zebedee said:


> 2) I'm only talking about motorway use, where there is little or no gear changing required.
> Dave


I assumed members would realise that means no appreciable hills. :roll:

Clearly you would not use CC on an Alpine Pass unless you were a complete donkey, but on the flat, and with only fairly gentle inclines to cope with it makes sense to use it . . . in conjunction with a small measure of the common sense several folk have mentioned already. :wink:

I have tried to beat it, both on the flat and on a long steady incline - and the CC always wins. 

Dave


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## Rosbotham (May 4, 2008)

Zebedee said:


> Zebedee said:
> 
> 
> > 2) I'm only talking about motorway use, where there is little or no gear changing required.
> ...


Maybe you have that in Worcestershire Dave, but such conditions don't exist around Lancs & Cumbria. M6 is a constant up/down of traversing river valleys, other than long straights e.g. between Preston & Garstang, which just has bunching traffic instead  .


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## Zebedee (Oct 3, 2007)

Rosbotham said:


> Maybe you have that in Worcestershire Dave, but such conditions don't exist around Lancs & Cumbria. M6 is a constant up/down of traversing river valleys, other than long straights e.g. between Preston & Garstang, which just has bunching traffic instead  .


That is very sad! 

You will just be forced to go to France on holiday so you can get the value out of your CC. :wink: :lol:

Just grin and bear it - you might even enjoy it!! :lol:

But seriously though, obviously not the best terrain for using cruise control. Probably not worth having - unless you do go abroad quite a lot.

Dave


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## CliveMott (Mar 10, 2008)

You justify fitting Cruise control on comfort criteria. Economy arguement is six of one and half a dozen of the other.

C.


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## lufc (Jun 24, 2007)

short-stick said:


> My observations...
> Cruise control cannot "see" hills and thus cannot anticipate and drive correctly for the conditions. Build speed gradually before a climb, reduce power before the peak but with enough momentum to get over the top and reduce power on the downhill... All good driving techniques. If cruise control cannot see what is ahead, it is only reacting, not predicting. I've driven with and without cruise control and in my experience, I save more fuel without cruise control.


On a recent run from Dublin - Belfast I did nto use CC and tried to keep a steady speed around 58-60 mph, anticipating hills and dropping out of 6th. This seemed to give a good return. On the way down from belfast - Rosslare I used CC and could see the needle dropping, so I tend to avoid using CC unless on a long flat road as I am convinced it is less economical.


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## gaspode (May 9, 2005)

I wouldn't want to go back to a vehicle without CC other than for a small runabout, it's one of the best extras ever invented for long trips. But is it more economical than a good driver? Of course it isn't, how could it be? It can only open the throttle when speed drops off, it has no way of assessing road conditions like a human brain. :roll: 

Used in the correct situations however I reckon that the difference can be so small as to be irrelevant and is more than compensated for by the more relaxed driving experience.


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## artona (Jan 19, 2006)

I have had cruise control on vehicles for years. One interesting aspect is that whilst most men will happily use it many women hate it. I think they feel they are losing control :lol: :lol: 

But back to the question zebs has asked as long as you do not simply abdicate the responsibility of driving to the crusie control you get many more miles to the gallon. I use it all the time on my 3 litre Saab and it returns on average 27 mpg. Shona never uses it on her 2 litre saab and only gets 21.

As much as the cost saving I think increased miles per gallon is also helping our planet in reduced fumes etc. Whilst my cruise control is on straight away I tend not to use it for the first few miles until the engine is warm, I will see hills ahead and take over, if approaching traffic lights I will take it off and try to slow enough to keep the vehicle moving until the red lights change etc etc.

I am not sure who said earlier that they did not know how to work out how many mpg they were getting because they buy fuel in litres (as we all do) but if it helps 1 Imperial gallon = 4.54609188 litres

stew


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## Rapide561 (Oct 1, 2005)

*Cruise*

Hi

Different day, but I still say cruise control is less economical than my right foot.

Russell


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## sallytrafic (Jan 17, 2006)

I don't want to be driving where the road is flat 

As to more or less economical - *less* almost by definition how can it be economical to keep to the same speed.

I do use my cruise control but am careful never EVER to use the resume button if I've had to brake.

"Press the RES switch .... the system will attempt to resume the speed that you previously set" and how  mine pours fuel in :lol:


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## Stanner (Aug 17, 2006)

*Re: Cruise*



Rapide561 said:


> Hi
> 
> Different day, but I still say cruise control is less economical than my right foot.
> 
> Russell


It may well be marginally worse but it can keep it up for far longer without having to think about it.

.............and judging by Frank's contribution it seem that too many cruise controls are set to be too sensitive. I have 3 different cruise controls on 3 different vehicles and none of them "pours fuel in".

Perhaps it is all down to how well they are calibrated.


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## Winz (May 1, 2005)

Some great comments so far!
I tend to use it on flat stretches of motorways and dual carriageways, especially in France, but I find it's better to knock it off when approaching a hill and try and maintain a steady throttle, allowing the speed to reduce slightly on the way up, then pick up after the summit and re-engage the cruise when it's back up to speed. 
It seems to work reasonably well, as I've been getting between 28 and 30 mpg in a 2.8 JTD most of the time. Mind you, I do have a light right foot and try to keep the speed below 60 mph


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## mikeT (May 1, 2005)

I fully agree with Short stick observations associated with Cruise control it cant see the hills I tend to switch mine off going up and down hills ,until I reach the same speed and then re use .I have also notice that my computer average MPG drops when the Cruise control is switched on !! I think that a light footed driver can get a bit more MPG on normal driving and that Cruise control is good for motor-way use. 
Apart from giving a more relaxed drive it sure helps on the old feet and legs. not much in it MPG wise .


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## bulawayolass (Jul 27, 2010)

Rosbotham sorry to say l disagree l do the M6 Jct 25 to jct 15 or 16 and find l get better fuel on cc than cruse control as it has a slight downhill flow/slope. Coming back though it is slightly worse due to the uphill.

I agree about comments on using the cc l didn't want a camper without it. 

I have been warned if the road is puddly don't use it as the sensors can cause skids. Have been told if the road is wet but not puddled it is ok.


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