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Wed 23 Jun 2010 00:16

Does cruise control use more fuel? - wazza

Does cruise control use more fuel?

This applies to modern cars. This is my style of driving a car without cruise control. I accelerate gently, not sluggish or harshly. When i get to my desired speed i lift my foot slightly off the accelerator so that i am cruising at the desired speed using as less fuel as possible. When i go down a hill i lift my foot off the accelerator and let gravity do the work. Only apply accelerator when required. (No i am not the type who does 56.00 mph on the motorway, i do like to drive my car to the full within legal speeds of course ;-) ) Imagine you are on the motorway with the cruise control set at 70 mph. You have to apply brakes which automatically disengages the cruise control. When you press resume does the cruise control make the car accelerate harder than normal hence using more fuel? On a long journey is it economical to use cruise control compared to manual input (your right foot)?

Edited by wazza on 23/06/2010 at 00:17

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Wed 23 Jun 2010 09:42

Does cruise control use more fuel? - dieseldogg

The appliance of science, or logic, or intelligence dictates:

(i) all systems reach an equilibrium

therefore unless one has over-accelerated lifting ones foot will cause the veh to slow down, until a state of equilibrium is reached.

(ii) An intelligent sympthatic driver will use LESS fuel than cruise control ....simple reason, ease off when approaching the crest of a hill, gravity assisted acceleration on the other side. Ditto if spotting delays ahead, slow down early ( coast) uses less fuel than continuing at a steady speed then braking.

However for some out there who accelerate up the rear of the car in front ,then brake.... & reapeat as necessary.... cruise control will save fuel.

etc

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Wed 23 Jun 2010 12:08

Does cruise control use more fuel? - skittles

Well my 15 year old ar used less fuel on cruise, it would accelerate on hills and deaccelerate down hills, it did not accelerate that hard when pressed resume. On a regular trip to Wales it uses 2, 3 mpg less on cruise.

My new car hasn't got cruise - I miss it!

My friends car has various settings, I guessing if you set the car on economy it will use less if you set it on sports it will use more

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Wed 23 Jun 2010 13:51

Does cruise control use more fuel? - davecooper

Wazza, I have adopted a very similar driving style to you. I constantly modulate the accelerator pedal pressure slightly. I can tell if the car is likely to slow even before it shows on the speedo, it has just become instinctive. It is amazing how often you can take pressure off without loosing any speed. This obviously mimics cruise control to some extent and I do get better mileage using this driving style. Whether cruise would be even better though I don't know.

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Wed 23 Jun 2010 14:46

Does cruise control use more fuel? - Andy P

Cruise control systems are always designed to accelerate using the most fuel-efficient application of throttle. If it used the "hoof it" approach, mine would drop down two gears every time I pressed the resume button.

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Wed 23 Jun 2010 15:32

Does cruise control use more fuel? - Glaikit Wee Scunner {P}

In the spirit of unification of this site and "elsewhere", I'd again say no.

Not if the cruise control is used to maintain a steady and relaxed cruise.

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Wed 23 Jun 2010 18:13

Does cruise control use more fuel? - NARU

>> Cruise control systems are always designed to accelerate using the most fuel-efficient application of throttle.

That is absolutely not true. My mechanic fiend tell me that on a 911 the system resumes the selected spped 'as rapidly as the car allows'.

And I don't think its true for ordinary cars either. Cruise control cannot see the road ahead - I regularly managed 3mpg better than the cruise control on long journeys (back when I was doing a 400 mile round-trip commute).

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Wed 23 Jun 2010 20:28

Does cruise control use more fuel? - Glaikit Wee Scunner {P}

When in the USA a few years back, I hired a 3.5l V6 petrol Toyota Avalon automatic.

With a bit of fiddling I found it had cruise control. Scarily though, when pulling up a long Arizona hill at the legal 75mph it started to slow down , and the automatic application of power made it drop down 1 or 2 gears. The consequent torque steer jerked the steering towards the dusty desert verge. An interesting moment.

But the cruise was generally a great boon and a rough calculation I made was 36mpg (imperial). Excellent for such a spacious car.

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Thu 24 Jun 2010 08:42

Does cruise control use more fuel? - Andy P

Okay, I'll rephrase it then - it seems to work that way on mine.

As for "seeing the road ahead", I don't see how that affects how the cruise control system works - after all, it's the driver that decides when to switch it on and off again.

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Thu 24 Jun 2010 08:46

Does cruise control use more fuel? - dieseldogg

Except

A driver applying a modicum of intelligence and therefore anticipation reads the road and traffic conditions ahead and modulates his throttle accordingly , why rush up to a rolling road block and then have to brake .................rather modulate the throttle furthur back and "freewheel" thus saving fuel, yes?

ditto for climbing hills etc etc, etc etc.

Cruise control cannot (yet) be intelligent

only reactive

simples

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Thu 24 Jun 2010 12:58

Does cruise control use more fuel? - Andy P

That's why I made the point about the driver being in control - I use CC a fair bit, but I don't use the "last minute braking" approach - if the traffic appears to be slowing I either knock CC off or use the speed reduction feature on the CC.

As with a lot of these "gadgets", they're only as good as the person using them.

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Thu 24 Jun 2010 14:44

Does cruise control use more fuel? - dieseldogg

ok cheers Andy
M

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Thu 24 Jun 2010 18:03

Does cruise control use more fuel? - a900ss

I think it's also worth bearing in mind that the true reason for CC isto hold a maintained speedand therefore make for a more relaxing drive when used appropriately.

This far outweights any slight decrease in cnsumption for me.

Edited by a900ss on 24/06/2010 at 18:03

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Thu 24 Jun 2010 21:22

Does cruise control use more fuel? - Roly93

Yes it does...

Careful 'manual' driving is far more economical.

My A4 on a nice warm day like today will do 52 ish at a steady 70-75, usin CC knocks at least 2MPG off this.

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Sat 26 Jun 2010 14:56

Does cruise control use more fuel? - julie page

Think cruise is a God send on long journeys

Unless you know a road really well I wonder how you can atticipate every incline or decline precisly. Cruise will keep the cars I have driven at a constant speed.

Anyone know if I can get cruise fitted to a RX8, been trying for ages

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