Cruise Control and Fuel Economy
Discussion
I believe the generic answer is that a good driver should be able to achieve better mpg than cruise control which just aims to maintain a set speed therefore may use full throttle to power up a steep ascent and not let off earlier in anticipation of a descent.
If you’ve got lead boots and don’t read the road ahead then I guess a decent radar cruise would help.
If you’ve got lead boots and don’t read the road ahead then I guess a decent radar cruise would help.
Halmyre said:
Is your fuel economy better or worse when using cruise control? What say the PH experts?
Depends on the setpoint. In eco, car activates cylinder deactivation more often when on cruise than when on full manual. If it's set to 60, it'll do way better than I do in terms of MPG - purely because I'll keep drifting up toward 70.
Set to 70, no difference really. Can't change the laws of physics.
Generally worse.
It knows how fast the car is going and can add / remove throttle.
That is about all - Barring ACC which can see the car in front and apply brakes (Not just for traffic - Also down hills etc?)
You can see the terrain for miles - Gently waft up this hill behind the truck, then use momentum on the other side to pass and get back up to cruise speed?
Lift off extra early for a clump of traffic?
Etc.
Even on quite empty, non-traffic dodging drives I'd say I can net a 2-3MPG gain over cruise control just by using terrain and forward planning.
It knows how fast the car is going and can add / remove throttle.
That is about all - Barring ACC which can see the car in front and apply brakes (Not just for traffic - Also down hills etc?)
You can see the terrain for miles - Gently waft up this hill behind the truck, then use momentum on the other side to pass and get back up to cruise speed?
Lift off extra early for a clump of traffic?
Etc.
Even on quite empty, non-traffic dodging drives I'd say I can net a 2-3MPG gain over cruise control just by using terrain and forward planning.
If no hills it's a close thing 2-5% difference.
But if hilly, manual throttle control wins easily (and by up to 10%) over cruise control.
The reason is that cruise control puts the brakes on (to maintain constant speed) going downhill (sapping energy) and as you arrive at the bottom of the hill at a now slower pace, cruise control will apply more throttle than manual application to get up hill at a constant prescribed speed.
We did this test in a Magazine about 22 yrs ago btw.
But if hilly, manual throttle control wins easily (and by up to 10%) over cruise control.
The reason is that cruise control puts the brakes on (to maintain constant speed) going downhill (sapping energy) and as you arrive at the bottom of the hill at a now slower pace, cruise control will apply more throttle than manual application to get up hill at a constant prescribed speed.
We did this test in a Magazine about 22 yrs ago btw.
it reduces the effort required to drive quickly, so worse.
if i drive a car without cruise, my foot gets a little tired of pushing the throttle pedal down for hours on end, hence i speed up and slow down a lot, and generally go slower, as that requires less pressure on the throttle pedal.
with cruise, however, setting the cruise at 70 takes exactly the same effort from me as setting it at 90, so i tend to set the cruise higher and get worse mpg as a result.
got to drive my wife to gatwick from the midlands on sunday - will likely set the cruise to 85 and just deal with the poor mpg - i'm claiming fuel expenses anyway.
if i drive a car without cruise, my foot gets a little tired of pushing the throttle pedal down for hours on end, hence i speed up and slow down a lot, and generally go slower, as that requires less pressure on the throttle pedal.
with cruise, however, setting the cruise at 70 takes exactly the same effort from me as setting it at 90, so i tend to set the cruise higher and get worse mpg as a result.
got to drive my wife to gatwick from the midlands on sunday - will likely set the cruise to 85 and just deal with the poor mpg - i'm claiming fuel expenses anyway.
I find cruise control is brilliant at maintaining speed compared to the human driver. But it probably comes at cost of fuel consumption as it will fine tune the throttle input to match the speed target precisely and always be burning ‘some’ fuel, whereas a human will ease off and let the speed dip before applying throttle again. Multiply by a few dozen over the course of a journey, and the cruise control will get to the destination earlier by maintaining cruise speed better, but will have burnt marginally more fuel in doing so.
I used to shy away from using Cruise Control as I found I got better MPG doing it all myself (about a 5mpg difference). Also annoyed me it would brake for me when going downhill rather than use the momentum and labour the engine a bit to get back up the hill.
Nowadays the roads which I travel on in these instances have become average speed camera roads so I just set my cruise control and forget about it. The couple of MPG difference doesn't bother me too much, but a ticket for not adhering to the averages would.
Nowadays the roads which I travel on in these instances have become average speed camera roads so I just set my cruise control and forget about it. The couple of MPG difference doesn't bother me too much, but a ticket for not adhering to the averages would.
Matthen said:
RazerSauber said:
That'll depend on your driving ability. If you're good at anticipation and understanding how to drive economically then cruise control will reduce your MPG. You'll gain MPG if you drive like a tosser.
Other way around.
Reduction in mpg = more fuel burnt.
DodgyGeezer said:
I'm happy to be told I'm wrong - however my understanding is that modern CC is actually more economical than the older/cruder type and, crucially, doing it yourself...
Almost certainly is, on a flat road with no traffic - it’ll be better at maintaining speed with minimal required throttle input. But throw in some hills (which it will increase throttle on to maintain speed, vs. slowing slightly with the same throttle input if you’re driving yourself) and a bit of traffic for it to anticipate and it’s not quite so clear. Gassing Station | General Gassing | Top of Page | What's New | My Stuff