Best Fuel economy: cruise control ON or OFF?

[HumberMart]

Can't say the idea of selective use of CC to keep engage it appeals much to me. Seems like to much like hard work.

I'll continue to use mine when it suits, recognising that it might reduce my average mpg from about 44 to 42.

Compared to the 7 to 10 K I'll lose in depreciation each year, 2 mpg is not worth a hoot.

I just find it a little strange how reluctant some people are to accept the facts about the impact of CC on economy.

 

[ItalianTuneUp]

Cruise control has always affected my mpg negatively, I'd say an average of 10% loss.

As an example I did a 200 mile round trip in my Q7 4.2 V8 TDI and on the way there I used my C/C as much as possible with the speed set at 72mph and achieved 28.7mpg. On the 100 mile journey back I didn't use the C/C at all and drove as I normally do (keeping up with traffic up to 80) and achieved 33.1mpg.

If the journey there had more inclines than on the way back, it's possible this could have something to do with the difference.

It would be interesting to do the round trip with CC on, then the next time you do the round trip have CC off.

However, other factors like head winds can also affect mpg, and these vary, so it's always difficult to know for sure

 

[ItalianTuneUp]

Well, you're right, I may find turning CC off for hills becomes too much aggro, and just leave CC on ;-)

 

[theogeor]

I just find it a little strange how reluctant some people are to accept the facts about the impact of CC on economy.

and the fact is some report better and some worse

one thing that we are not considering is the engine and gearbox characteristics at the cruising speed. not all cars/engines will bahave the same at lets say 70mph.

with my 911 I have seen again and again better MPG when cruising with CC on but to be fair on my dads Octavia I did not get the same. big difference is that at 70-80mph the 911 is not even half the top speed and is effortlessness for the engine and CC to maintain that. On the other hand a different car with less power and similar weight will require a lot more throttle adjustment to maintain the same speed

Theo

 

[geraldrobins]

To be honest Ive not read any facts just opinions in the main. I do accept that using CC isnt the mose economic drive, but if economy was my main interest Id drive at 50 ish.

 

[Frugal]

I agree with the various posters who have pointed to constant throttle being more fuel efficient than constant speed and that the two become very close when the road is flat and you aren't having to adjust for traffic. Interweb searches for nempi, hypermiling, wayne gerdes etc throw up much the same information and several sites refer to 'driving with load'. Also 'pulse & glide' is a technique that's possible when CC not engaged but even though I like to drive efficiently I'm not sure I could be bothered with this one tbh ...

 

[Deleted member 65149]

Not hard for millions of drivers without CC.

It's just intuitive. You become oblivious to worrying about the slower up hills and quicker descents. In fact if you use CC on a road with lots of concurrent rise and falls it tends to feel like the car is accelerating on the up hills, even though it's not. Most drivers without CC keep their foot pretty still and avoid the consistent squirts of fuel that CC uses to maintain a fixed speed.

Like AC, just accept it uses more fuel but it's worth it for the comfort.

Millions of motorists MAY keep their right foot pretty still on the throttle, but I very much doubt it. I'm sure I'm not alone in observing the wide variations in speed of a high proportion of other motorists when I'm driving with CC on. And this is on long flat sections of road.

But economical driving isn't about keeping the throttle steady, it's about knowing how much to ease off the throttle whilst maintaining the same speed. I would suggest that most motorists DON'T do this, instead they generally continue to burn fuel unnecessarily by keeping the throttle pressed slightly more than is needed. CC provides no more than the quantity of fuel required to maintain a steady speed, so it must be better than the average driver on level or nearly level roads.

Of course there are many other methods of reducing fuel usage, such as looking well ahead to reduce the need for braking and subsequent acceleration, and most of these will have more effect than CC on or off.

 

[baxlin]

But economical driving isn't about keeping the throttle steady, it's about knowing how much to ease off the throttle whilst maintaining the same speed. I would suggest that most motorists DON'T do this, instead they generally continue to burn fuel unnecessarily by keeping the throttle pressed slightly more than is needed. .

Mrs Baxlin has a 1.2 3 cyl Skoda Fabia, which is, IMHO, underpowered, but it does illustrate this point perfectly.

As it's underpowered, there's the temptation to use more pedal pressure than necessary, but easing off a tad sends the MPG immediate readout skywards, without always dropping the speed. Watching the readout, although distracting, improves the mpg considerably.


Just wish Mrs B would look at it occasionally............................