Afternoon all!

On my now very quiet daily drive to work I've been pondering whether cruise control gives better economy or not than the old foot control.

Driving for 15 miles down a deserted A1 at 65 mph using cruise and monitoring the instantaneous figures looks like it's slower to get to 99.9mpg on downhill bits than is that case if I'm driving manually.

What's everyone's opinion on this?  I might do some science and brim the tank (which'll cost about £4.53 at the moment) and then do some A/B testing.

It would be good to get others' thoughts on this!

Cheers!

Cruise control can't predict what's in front of it, so is reactive, whereas a decent driver can give a little momentum to an approaching hill or ease off near the top, etc. Cruise control on a long flat road should be fine and stop pedal drift as I call it, of folk being slightly heavy now and then or easing off.

My opinion of course

 

 

Cruise control for me saves the most fuel, that's on a 180 road trip both with and without, I can get close to 65-70mpg with the car with it enabled, driving on a reasonably quiet dual carriageway, newly serviced and a full set of new tyres. Time of day also makes a difference due to temperature and atmospheric pressures. 

For me though it's not so much the fuel savings but rather it's saves me mental energy on long distances and allows me to concentrate more on the road ahead than watching the speed I'm doing especially round speed traps. I do wish the car had adaptive installed but I'll settle for what I have.

Feet, and indeed whole humans, are pretty useless, they get tired, bored and distracted fairly quickly...

On a short stretch where you're fully alert, foot control is definitely more efficient.  In the real world, for the majority of the time, cruise is more efficient.

I use it every single drive for comfort and I'm pretty anal about mpg!   Wouldn't buy a car without now...have retrofitted it to a couple of previous cars too.

 

lots of people think cruise uses lots of fuel... its a myth it always uses less.

people are addicted to movement....   same when you're a baby, moving them about calms them down... cruise uses just enough to maintain the speed....  what virtually ALL drivers do is accelerate continuously, then brake, then speed up wasting fuel. 

The only bit cruise gets wrong is hills.... wastes gravity on the way down and argues with it going up hill.   These days with sick councils hiding cameras on hills its can save a speeding ticket though !

your experiment is not valid as it needs to be under the exact same conditions....  (which is impossible, wind speed and direction, ambient temp, humidity, atmospheric pressure, engine temp, all become players... )  you could try to average over a year of the same commute, but you may have better things to do in your life ?

11 minutes ago, Botus said:

The only bit cruise gets wrong is hills.... wastes gravity on the way down and argues with it going up hill.   These days with sick councils hiding cameras on hills its can save a speeding ticket though !

Yeah, that's the main reason I use mine when I can. Once bitten..............😀

19 hours ago, Botus said:

These days with sick councils hiding cameras on hills it can save a speeding ticket though !

Just be aware that it doesn't prevent the car from going above the set speed downhill as it relies solely on engine braking and doesn't apply the brakes.

5 minutes ago, mjt said:

Just be aware that it doesn't prevent the car from going above the set speed downhill as it relies solely on engine braking and doesn't apply the brakes.

Which really bugs me.  My 2008 C class didn't have active radar or other active cruise but it would apply the brakes when going down hill.  I'm sure Ford could do this but I'm not paying for a driver assistance pack full of other things I don't want.  Braking should be on all standard cruise packages now.

55 minutes ago, mjt said:

Just be aware that it doesn't prevent the car from going above the set speed downhill as it relies solely on engine braking and doesn't apply the brakes.

Yes, it's surprising how quickly it will pick up speed even on a fairly gently undulating road, so you certainly still need to keep an eye on the speedo. After many years of diesel driving I still haven't fully come to terms with the lack of engine braking on a petrol turbo.

20 hours ago, Botus said:

but you may have better things to do in your life ?

Right now...?  Lol

Thanks for all the replies!  It seems that cruise is the way forward for efficiency, exempting the hill case of course.

Just trying to work out if plod would accept further experimentation as "essential"

I have slight reduced mobility in my right ankle, my foot doesn't bend up as far as it should, and on long journeys with it in the same position it can ache.  Cruise is great for this.

56 minutes ago, Guy Heaton said:

I have slight reduced mobility in my right ankle,

Snap! Though mine more affects side to side movement so put an end to my heel and toe tricks!😀

I've found using the limiter set to 30/40 has improved my economy a reasonable amount. The car can read probably fractions of a mile per hour, so can very finely adjust the actual throttle value getting sent to the engine, whereas a human needs to attentively monitor the speedo needle and wait for it to move etc.

On ‎4‎/‎29‎/‎2020 at 10:18 AM, mjt said:

Just be aware that it doesn't prevent the car from going above the set speed downhill as it relies solely on engine braking and doesn't apply the brakes.

this is how old cars were... and IS how the mk2 does it. 

With the advent of ESP bringing the ability to try and stop itself spinning, it means the car has the ability to brake automatically.  To do this the ABS module grew its own brake pump.  On many current cars this does brake the cruise going downhill... ALL BMW and E class Mercs had this since 2007 (where fitted with cruise).  Its a free extra you get from ESP (although not all bothered to implement it).  And on many Autos from 1999 the electronically controlled box would recognise a hill and down change for you, pretty much bringing speed control on the way down.  

On 4/29/2020 at 11:17 AM, Eric Bloodaxe said:

Yes, it's surprising how quickly it will pick up speed even on a fairly gently undulating road, so you certainly still need to keep an eye on the speedo. After many years of diesel driving I still haven't fully come to terms with the lack of engine braking on a petrol turbo.

Mine does do engine braking (turbo petrol auto) when going down a hill to try and keep the speed below the set amount, but most of the time it's annoying/useless.

I remember once applying cruise control to 30 on a long downhill road with a speed camera on it, thinking the car would brake to maintain the speed. Instead it only downshifted, but it was utterly useless and I suddenly found myself going 35 past the speed camera. Oops!

On cars (unlike trucks or buses) engine braking is nowhere near as effective as normal braking is, it only works on very gentle inclines, and the increased revs is also annoying.

I don't think with mine. 3 cylinder 1.0 ecoboost, there is much engine friction to have much effect in engine braking