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Don;t  know if this question has been asked before, but I have just found out how to work cruise control on my fun car.  Has anyone ever experimented to find if there any difference in fuel consumption by using cruise control compared to manual operation of throttle at same speed?

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CC will be gentler on the 'throttle' and will save fuel.  Except downhill where it might not coast - will test soon.

On uphills cc will save compared to maintaining constant speed manually.  @xtrailmanhow can cc use more fuel on uphill sections?

Skoda Yeti 2.0 Outdoor DSG.  Freedom Jetstream Sports Twin Flare.  Reich mover.

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Depends on the vehicle.

 

My old BMW would brake downhill then accelerate uphill for example. Not fuel efficient.

Edited by logiclee
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Yeti 2.0TDi DSG 4X4 L&K, Octavia TSi Manual, Citigo ASG, Swift Challenger.

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Not noticed a lot of change in mine and it doesn't spent enough time in cruise to make a worthwhile difference anyhow.

                      Stay safe - Griff.:ph34r:

Discovery 4 with a Bessacarr 845 behind

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If you are on an undulating road CC will try it’s utmost to maintain that set speed. It will do that by increasing the amount of throttle, that will use more fuel. If not on CC a driver can allow the speed to bleed off as the car ascends the hill without increasing the amount of throttle applied. 

These days I think the difference is pretty marginal. What is good about CC is that it makes for a more relaxed long distance drive. Automatic CC is even better, yiu set the distance you wish to maintain to the vehicle in front and your speed. If the car in front slows then your car slows to match it. If the vehicle in front speeds up to beyond your set speed it pulls away. 

I have Auto CC on my car, if the vehicle ahead of me brakes so does my car (very spooky indeed) it’s fairly “enthusiastic” when it does so which I imagine is a deliberate feature to attract drivers attention. It’s cuts out at about 18mph with a warning sound, 

When on CC and going downhill my car will also brake in order to maintain the set speed as well.

I use CC a lot in 30/40/50 limits, it’s a licence saver! (I also have speed limiter fitted but prefer to use CC) 

Experience is an awful teacher who ends up sending you simply horrifying bills

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8 hours ago, madam val said:

there any difference in fuel consumption by using cruise control compared to manual operation of throttle at same speed?

So, to answer the OP - cc will save fuel because it will be gentler on the gas.

Skoda Yeti 2.0 Outdoor DSG.  Freedom Jetstream Sports Twin Flare.  Reich mover.

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1 hour ago, xtrailman said:

Unless on a level road cc will use more fuel, ACC  even more.

 

25 minutes ago, Mr Plodd said:

If you are on an undulating road CC will try it’s utmost to maintain that set speed. It will do that by increasing the amount of throttle, that will use more fuel. If not on CC a driver can allow the speed to bleed off as the car ascends the hill without increasing the amount of throttle applied. 

These days I think the difference is pretty marginal.

 

 

The first statement is ambiguous, because it depends on the driving habits of the individual

 

Assuming the driver in control is attempting to maintain a constant speed they will also need to increase the engine revs on an uphill gradient, however the CC will be a more controlled and gradual ramp up via the EMS whereas the driver may waste more fuel by use of the accelerator pedal, such as overcompensation.

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In my experience, CC uses more fuel. Not scientific, but that's what I find.

The only explanation I can come up with is that downhill CC uses very light throttle whereas human control inevitably, under those conditions uses a "burn and overrun" method, and while in overrun modern engines use no fuel at all.

41 minutes ago, kelper said:

So, to answer the OP - cc will save fuel because it will be gentler on the gas.

How do you know that CC will be "gentler" on the gas than the OP's right foot?

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fwiw ...

Yes, have experimented lots on the 1650mile each way motorway / Peage Winter run towing to SE Spain & back. Lots of undulations especially in Northern & mid France.

Well loaded 2013 MB W166 ML 250 7 speed auto & 1500kgs s/a Caravan - usually 85/92 kmph. Car dash display will show & reset my mpg economy as & when desired so can check on regular basis.

Concluded for me :-

When on a steady road with little traffic CC = more economical (& is less stressful). 

When on steeper undulating areas CC = uses more fuel (& is more stressful). Engine changing down and revving hard to try & maintain speed on ascents. Downhill and some Engine breaking but brakes also coming on to reduce speed. So usually switch off CC, just speed up a bit when approaching a hill but slowly easing off on ascent as speed reduces naturally to crest. Lock into a lower gear for improved engine breaking on descents. 

In heavier traffic don't normally use CC as too stressfull.

All assists with any mild boredom en-route !

 

PS Towing front covers. Equally for interest have found on test, (on very similar level area of road & temps) 2 hours with Towing front cover fitted / 2 hours removed  - improved economy 10% (back to expected mpg) without Cover & mild droning noise went - please discuss ?  

Regards to all in these strange times.

M

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I think it depends on the exact comparison you are making. If comparing CC with a person trying to exactly replicate the performance of the CC i.e. maintain a very constant speed, then I believe CC may do a more efficient job. However in a real situation the human may be more sympathetic and consciously or not when the vehicle has to work harder will drop below the 'set' speed and hence might perform better.

I suspect however in most circumstances the difference will be small enough to not matter unless the human driver is very heavy footed in which case CC will be better. The biggest advantage is how much more relaxing it can be to use CC.

The technology in different cars will also have an effect with some being smarter than others.

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Life is not a rehearsal . . .:)

Porsche Cayenne S Diesel & Knaus StarClass 695. Previously Audi S4 Avant & Elddis Super Sirocco

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58 minutes ago, KnausCol said:

I think it depends on the exact comparison you are making. If comparing CC with a person trying to exactly replicate the performance of the CC i.e. maintain a very constant speed, then I believe CC may do a more efficient job. However in a real situation the human may be more sympathetic and consciously or not when the vehicle has to work harder will drop below the 'set' speed and hence might perform better.

I suspect however in most circumstances the difference will be small enough to not matter unless the human driver is very heavy footed in which case CC will be better. The biggest advantage is how much more relaxing it can be to use CC.

The technology in different cars will also have an effect with some being smarter than others.

:goodpost:

 

To a degree having CC set takes away the temptation to put my foot down for some 'spirited' driving, so can decrease my fuel consumption. I use it on most roads (solo).

2018 Octavia vRS 245 TSI Estate & 2016 Adria Altea 552 DT Tamar

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Don’t know as I always use ACC, I was using it in town recently when the car in front slowed and as I slowed down I expected to get the warning at 20mph and for it to cut out but it actually brought the speed right down to about 1mph then as the car in front moved away it kept up with it.

 

Read the manual when I got home and it is called queue assist so played with it and it will bring the car to a complete stop if needed and displays “car held” and you just need to touch the accelerator and it accelerates back to the set speed.

 

It also has off road cruise which can be set in 1mph increments up to 20mph and it works both uphill and down.

 

Ian

2018 Range Rover Sport AB,  2015 Buccaneer Cruiser.

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The DAF HGV I drive rates my driving, awarding up to 5 ticks if it thinks I've done well on several metrics. One of the things I get ticks for is using cruise control. After about an hour on cruise it'll give me 5 ticks for saving fuel. So DAF clearly think it saves fuel over me just keeping my foot welded to the floor. 

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The longer you use cc on the Daf’s the more your performance score percentage  goes up.

Duncan

Edited by DUNCAN123
Miss spelled

61 Santa Fe & 2011 Bailey Olympus 624

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All I can say is, being an owner of 2 Mitsubishi Outlander's over the last 5 years (both forecourt new). A week before lockdown we had to attend a funeral at Rayleigh, between Basildon & Southend on Sea, some 210 miles one way from home. After navigating our home town and getting onto dual carriageways, the only time out of cruise control, was a road change. Recording an average of 56mpg, which I have never seen on these 2 cars. An indicated 68mph maximum, with a 48mph on the M4 roadworks by Reading, 2 up and a small overnight bag. It works for me. (Cruise with speed limiter)

Swift Elegance 480, towed by a Mitsubishi Outlander GX4 Automatic.

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I drive a land rover so I don’t look at mpg at anytime......it will only upset me😧 only use cc on the motorway if I remember too.

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1 hour ago, Ironeddie said:

The DAF HGV I drive rates my driving, awarding up to 5 ticks if it thinks I've done well on several metrics. One of the things I get ticks for is using cruise control. After about an hour on cruise it'll give me 5 ticks for saving fuel. So DAF clearly think it saves fuel over me just keeping my foot welded to the floor. 

 

A lot of the newer truck CC's are very clever, even using GPS so they predict the most fuel efficient way to get down an incline, round a slight bend and get up the otherside.  And they may even sacrifice some speed to achieve that.

 

Car  systems are much more variable.  Some brake, some don't, some have fairly smooth acceleration rates and some take off like a scalded cat. Probably why there's many differing opinions.

Yeti 2.0TDi DSG 4X4 L&K, Octavia TSi Manual, Citigo ASG, Swift Challenger.

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??? HGVs are supposed to be limited to 56mph, so what difference does a CC make if speed set to 56, over driver flooring it.

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10 minutes ago, madam val said:

??? HGVs are supposed to be limited to 56mph, so what difference does a CC make if speed set to 56, over driver flooring it.

 

Read my post above. The CC systems on modern trucks have GPS data including incline data. they know when to coast, when to shift and when to sacrifice speed in the interest of economy.

 

http://tools.mercedes-benz.co.uk/current/trucks/pdfs/trucks/actros/truck-and-drive-reprint.pdf

 

The article is 6 years old, these system are now wider spread and more advanced.

 

 

Edited by logiclee

Yeti 2.0TDi DSG 4X4 L&K, Octavia TSi Manual, Citigo ASG, Swift Challenger.

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3 minutes ago, logiclee said:

 

Read my post above. The CC systems on modern trucks have GPS data including incline data. they know when to coast, when to shift and when to sacrifice speed in the interest of economy.

 

http://tools.mercedes-benz.co.uk/current/trucks/pdfs/trucks/actros/truck-and-drive-reprint.pdf

 

 

If I covered as many miles a year as trucks are designed for I would also be keen on saving every percentage point in fuel consumption!

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On 21/09/2020 at 07:47, Dave Capiro owner said:

How do you come to that conclusion?

 

No coasting with ACC in use,  ACC will keep your speed checked going down hill which wastes fuel and it does not allow any drop off of speed when climbing a hill, fuel can be saved by slowing down and speed gained at no cost to fuel when going down hill.

 

ACC is even worst as it will brake the car down hill or if a car cuts in front to regain the gap set.

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14 hours ago, logiclee said:

 

A lot of the newer truck CC's are very clever, even using GPS so they predict the most fuel efficient way to get down an incline, round a slight bend and get up the otherside.  And they may even sacrifice some speed to achieve that.

 

Car  systems are much more variable.  Some brake, some don't, some have fairly smooth acceleration rates and some take off like a scalded cat. Probably why there's many differing opinions.

 

That's correct cars have crude systems compared to the systems used on modern trucks, the system you describe covers exactly my dislikes with car systems which don't save fuel in ACC.

They are good though at maintaining a set speed.

 

 

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