Cruise Control and MPG

FreddieFrugal

Hello there,

I was wondering whether any drivers with Cruise Control on their cars could share their experiences with it, with regard to fuel consumption.

I was all for getting a car with cruise control when we next change vehicles as I could see the benefit of giving the foot a rest on very long journeys.

However I'm unsure as to how economical it is to run. I assumed that if it the computer was tuned correctly then in theory it could be more economical to use.

When we went on holiday this summer I was renting a car, Opal Corsa, which had cruise control. But I found that engaging cruise control under any conditions (uphill, flat or downhill) resulted in a dramatic increase in fuel use. It felt more like an overdrive button.

The fuel consumption would be nearly double under some conditions. And was always using at least 2 litres of fuel extra according to the readout on trip computer.

Is this typical? Or was there just something wrong with the cars cruise control.

DUTR

IanRi wrote: »

Hello there,

I was wondering whether any drivers with Cruise Control on their cars could share their experiences with it, with regard to fuel consumption.

I was all for getting a car with cruise control when we next change vehicles as I could see the benefit of giving the foot a rest on very long journeys.

However I'm unsure as to how economical it is to run. I assumed that if it the computer was tuned correctly then in theory it could be more economical to use.

When we went on holiday this summer I was renting a car, Opal Corsa, which had cruise control. But I found that engaging cruise control under any conditions (uphill, flat or downhill) resulted in a dramatic increase in fuel use. It felt more like an overdrive button.

The fuel consumption would be nearly double under some conditions. And was always using at least 2 litres of fuel extra according to the readout on trip computer.

Is this typical? Or was there just something wrong with the cars cruise control.

Perhaps it is because the Corsa has a small engine? I remember similar with a Clio on holiday using air con, it just zapped the power from the engine.
My current and previous car have CC, using CC has no negative effect on fuel consumption, if anything it is better. Some ignorant people will claim that it gives full throttle to resume speed, I fear these type do not understand the cars are designed by engineers, not a bunch of muppets guessing poking and hoping.
And yes I tried resuming to 70mph from about 25mph and it is a gentle acceleration in any gear chosen.

A._Badger

DUTR wrote: »

Perhaps it is because the Corsa has a small engine? I remember similar with a Clio on holiday using air con, it just zapped the power from the engine.
My current and previous car have CC, using CC has no negative effect on fuel consumption, if anything it is better. Some ignorant people will claim that it gives full throttle to resume speed, I fear these type do not understand the cars are designed by engineers, not a bunch of muppets guessing poking and hoping.
And yes I tried resuming to 7mph from about 25mph and it is a gentle acceleration in any gear chosen.

Ditto with a 2 litre Honda petrol engine. No appreciable difference.

Master_Blaster

Probably typical due to the way it works. It is designed to maintain a constant speed, so it will start to accelerate when it senses a loss of speed once the effect of an incline is felt so no gradual build up on the approach. Same is also true when descending braking is applied when the speed starts to increase rather than the driver just easing off at the top of a slope.

forgotmyname

If your a good driver then you should be able to get better mpg without the cruise control but the actual figure will be small.

Too high a gear with too little torque for the incline will need more fuel.

Iceweasel

The sole purpose of Cruise Control is to maintain a constant speed.

Giving your right foot a rest isn't part of the plan and neither is to improve fuel consumption.

I use CC a lot on long journeys and find it makes little or no difference to my fuel consumption if I'm travelling at a steady 70 mph for example.

I find on motorways where there are slight uphills and down that I catch up on people who slow up on hills and then they pass me again on the down slope.

That happens irrespective of the way that I drive, either with CC or not, as without CC engaged I give the car more accelerator to maintain speed on the ups and I ease off on the down-hills so I run at a steady speed whatever.

Was the Corsa you had a manual or an auto.

CC on a manual often means that the car is in the wrong gear and many people are reluctant to disengage CC, change gear and then re-engage CC.

colino

Depends on the car and the system. Jaguar XF seems to save fuel on long-distance runs, whereas Mercedes E Class seems to think that cruise is a signal that petrol is going out of fashion.

AdrianC

Whether cruise is more or less economical than manually controlling speed depends entirely on the _driver_, no more, no less.

As Iceweasel says, all cruise does is to keep road speed constant. If the road goes up an incline, it'll use more throttle when the more economical action may be to let speed bleed off slightly. If the road goes down an incline, it'll close the throttle, when allowing speed to climb may build momentum for the climb coming up.

Alternatively, if the driver is one of those who cannot keep a steady speed to save their lives, constantly accelerating and decelerating, then cruise will almost certainly save fuel. But so would learning to drive.

DKLS

I use CC a lot, and have no idea if it has an effect on MPG, as I don't actually know what MPG my current car does nor have any interest in knowing, as soon as I get to a qtr of a tank I fill it up.

sh0597

It shouldn't make a noticeable difference.

harveybobbles

What about cruise control with the aircon on, the sunroof open and a boot full of luggage?