Does cruise control affect fuel consumtion?

ncmc

Just wondering if having your car on cruise control affects the fuel consumption of your car (either positively or negatively)?

bazz26

I find it has a positive effect on fuel consumption as the car is travelling at a consistant speed where there is no strain on the engine. On the other hand if you are climbing a hill the cruise control will adjust to keep at that set speed, increasing the throttle and hence using more fuel.

Don't think it makes a massive difference to me though to be honest as on my daily commute there are stretches where you usually run into heavy traffic or types of roads where cruise control cannot be used. On a motorway with little or no traffic it is great though.

Fey!

I've heard people say that it does, but I've never noticed it in either of the cars with cruise control that I've owned (Honda Accord and BMW 520), or in any of the others I've driven (BMW 525, C-Class Merc...)

peasant

It can affect it either way, depending on your driving style.
If you're one of those "digital" drivers that has the loud pedal either on or off, cruise control will lower your fuel consumption.

On the other hand, CC can't read the road and will just keep the speed regardless, so if you want to be really thrifty and maximise economy you'll have to switch it off.

mickdw

CC will use more fuel than person driving economically. One main reason is that is will apply brakes on downward slopes to hold the car at set speed whereas if being manually controlled, the driver would tend to allow a little increase in speed thereby taking advantage of the 'free energy' from the hill

Stephen

I find using cruise control to be more economical on motorways and the like. On regular primary roads with all the traffic and what not it makes little difference in my experience.

niceirishfella

Cruise will burn more fuel on most cars as opposed to steady manual driving.

Steve

mickdw wrote: »

One main reason is that is will apply brakes on downward slopes to hold the car at set speed whereas if being manually controlled, the driver would tend to allow a little increase in speed thereby taking advantage of the 'free energy' from the hill

I've never seen CC that could control the brakes

Unless you're talking about hybrid regenerative braking?

ART6

stevec wrote: »

I've never seen CC that could control the brakes

Unless you're talking about hybrid regenerative braking?

Me neither. I would expect that it would reduce the throttle setting and so apply an element of engine braking, which would have the same effect on fuel consumption as allowing the car to benefit from gravity on a downhill slope.

JHMEG

stevec wrote: »

I've never seen CC that could control the brakes

The latest generation of CC, loosely dubbed Adaptive CC, as used by Lexus, Honda, Audi and others, can and does. In most cases these cars have collision avoidance as part of the CC system.

http://auto.howstuffworks.com/cruise-control4.htm

http://www.engadget.com/2008/02/18/volvo-mercedes-and-honda-get-tested-for-collision-prevention-e/

MrPudding

stevec wrote: »

I've never seen CC that could control the brakes

Unless you're talking about hybrid regenerative braking?

I had the lend of an S class for a few weeks and it would apply the brakes to keep at a constant speed. It did not have the adaptive CC that would slow you down if it detected a car in front, it simply applied the brake if you were going faster.

MrP

Wishbone Ash

I find it difficult to tell if it is more economical because it's generally used it on longer journeys which are more economical anyway.

Steve

Well ye learn something every day:)

I've only seen this in the GS450h, it doesn't use physical brakes, it regererates to slow you down - even when you first press the brake pedal. The actual brakes dont apply unless they're needed.

Green Hornet

My Civic has CC and I can feel the "braking" going downhill. Often wondered did I look like an idiot with brakelights flashing every few minutes going downhill. However, the brake lights do not come on because the brake pedal is not depressed. The brake light is activated at the brake pedal.

nialler

I Find the CC more economical but on our roads it's difficult, even on motorways you're lucky to go on a 10 min stretch without some idiot either A - blocking you in or B - suddenly stuck in the RHL when you're going to overtake, thus having to hit the brakes and disengaging the CC.

My 8 year old S Class either brakes or engine brakes to keep at a constant speed, it's more noticeable when you put the limiter on and fly up to 60kmh and it's like when they turn the throttle down in an aircraft, you get that slight negative G feeling, very weird.

Green Hornet

nialler wrote: »

I Find the CC more economical but on our roads it's difficult, even on motorways you're lucky to go on a 10 min stretch without some idiot either A - blocking you in or B - suddenly stuck in the RHL when you're going to overtake, thus having to hit the brakes and disengaging the CC.

True. In Ireland you only get limited opportunities to use it. The only thing is that you can use the "Up or down" function to keep resetting it but thats only useful for small adjustments rather than long term speed control and eventually you will end up as Nialler's post says.

bman

Green Hornet wrote: »

My Civic has CC and I can feel the "braking" going downhill. Often wondered did I look like an idiot with brakelights flashing every few minutes going downhill. However, the brake lights do not come on because the brake pedal is not depressed. The brake light is activated at the brake pedal.

Isn't the idea of the brake lights to indicate to other roadusers that you are applying the brakes and therefore slowing down (or in the case not speeding up due to the gravitational force of going down the hill)? IMO the brake lights should be activated in this situation to notify the person behind. Seems a bit irresponsible of the car manufacturer.

Green Hornet

bman wrote: »

Isn't the idea of the brake lights to indicate to other roadusers that you are applying the brakes and therefore slowing down (or in the case not speeding up due to the gravitational force of going down the hill)? IMO the brake lights should be activated in this situation to notify the person behind. Seems a bit irresponsible of the car manufacturer.

Not really because you are not slowing down.

You are going at exactly the same speed all the time that the CC is on. In other words if its set to 65 the car will do 65 whether going up or down a hill.