Cruise Control and MPG

Herzlos

It might be because the car is struggling to maintain the speed, as said it's a pretty primitive system with no context of what's going on. Say you're cruising at a comfortable speed in top gear and hit a steep incline, you might then slow down enough that it's labouring in that gear to accelerate and will be wasting fuel.

I've only used it in bigger engined cars rather than rental Corsas, so I suspect that's what's happened.

I found it saved fuel on long motorway stretches, because A. it prevents the speed creeping up and B. it forces you to think a bit further ahead in order to maintain the speed.

They are also brilliant if you are stuck in a long stretch of roadworks with average speed cameras.

dannymccann

My diesel Mondeo 'appears' to use more fuel under CC than without it, but that is because it is constantly maintaining that set speed, regardless of inclines, declines etc. As already said, anticipation and reading the road ahead (something CC cannot do, yet anyway) will always win - using CC as much as I can in my car sees my average MPG fall to low 40's, whereas manual driving (because I read the road ahead, ease off well before roundabouts etc) will see my average start pushing up to high 40's - a great achievement in a 2.0TDCI Mondeo, which for some reason is very thirsty in standard trim

jaydeeuk1

When clarkson drove that audi a8 he found he got more mpg with cruise control off on the motorway and that was with a huge diesel engine

jimjames

forgotmyname wrote: »

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.

I find the same in my Golf.

Based on the dash readings my MPG is higher than when cruise is active

getmore4less

You can modify the behaviour of the CC.

if approaching an incline just accelerate a bit as you would normaly and the same on the downhill to avoid excessive engine breaking.

on the level lift and you return to your selected speed.
(most systems don't knock off the CC going faster just when you dab the brake)

You should not be using CC where speed control of the car is needed like approaching a roundabout with CC on I mad, flick it off and drive the car.


What I have found is I just go slower with CC on that saves loads.

Experience has shown that knocking 10mph of on a trip costs a tiny amount in time but gives far better economy.

DUTR

getmore4less wrote: »

You can modify the behaviour of the CC.

if approaching an incline just accelerate a bit as you would normaly and the same on the downhill to avoid excessive engine breaking.

on the level lift and you return to your selected speed.
(most systems don't knock off the CC going faster just when you dab the brake)

You should not be using CC where speed control of the car is needed like approaching a roundabout with CC on I mad, flick it off and drive the car.


What I have found is I just go slower with CC on that saves loads.

Experience has shown that knocking 10mph of on a trip costs a tiny amount in time but gives far better economy.

What if you have adaptive cruise control? As well as set the speed, you can set the distance from the vehicle in front.

getmore4less

DUTR wrote: »

What if you have adaptive cruise control? As well as set the speed, you can set the distance from the vehicle in front.

Even madder in the circumstances like approaching a roundabout.

gingerdad

dannymccann wrote: »

My diesel Mondeo 'appears' to use more fuel under CC than without it, but that is because it is constantly maintaining that set speed, regardless of inclines, declines etc. As already said, anticipation and reading the road ahead (something CC cannot do, yet anyway) will always win - using CC as much as I can in my car sees my average MPG fall to low 40's, whereas manual driving (because I read the road ahead, ease off well before roundabouts etc) will see my average start pushing up to high 40's - a great achievement in a 2.0TDCI Mondeo, which for some reason is very thirsty in standard trim

would second that, 2-3mpg difference

wasn't as bad in my previous Mazda 6 and could get 45 mpg easily, have to really try hard in my new mondeo to get mid 40's..

mcpitman

I've had both a vec-c and an now an insignia with c/c. Both appear to return better fuel economy when c/c is used when calculated on a brim to brim calculation

This is with both being driven with climate control on and diesel engines.

Used for 200 miles per day mainly on motorways.

Now also used in 30 and 40mph zones where the road is clear enough and not stop/start. (due to recent attendance of a Speed awareness course ).

Ebe_Scrooge

Herzlos wrote: »

They are also brilliant if you are stuck in a long stretch of roadworks with average speed cameras.

I don't use the CC on my car all that often, but I agree in this situation it's brilliant ( or it the traffic is heavy, then I use the speed limiter option instead ).

I think if you're doing a long stretch on a motorway that's fairly level then you won't notice much difference in MPG. But where you're in a hilly area - as others have said, CC will try to maintain a constant speed, which is not the most economical way to deal with hills. I always tend to use a gentle right foot, let the speed drop gradually on the uphill stretches, and where possible use the momentum from the downhill bits to help you up the next hill. If you tried to "manually" maintain a constant speed, you'd be accelerating hard on the uphill bits, and braking on the downhill bits, which is very wasteful.