Cruise Control vs no cruise control

[Brookied]

Hi Guys, 

So after a few months and a number of filling the car from bottom to top I am curious on a couple of things that you fine folk may be able to help with. 

based in Ireland so figures are km's, fill up details and range below.  (rounded up the figures below!)

Range    Litres Added    l/100km         MPG
900               53.82                 5.9          48.13
870               53.79                 6.2          45.69
885               54.33                 6.1          46.01
896               55.16                  6.2         45.89
847               55.87                 6.6         42.82
833               53.00                6.4         44.40
870                56.43               6.5          43.55

So. during the middle of the fill ups i got into the habit of using the active cruise control  on the way to work and back from work,  its a duel carriageway so can cruise ok however my feeling was that it impacted the range a little.   My last fill up was NO cruise control used at all and the range increased again and hitting near 900km per tank.  Time between fill ups is between 2 and 3 weeks. overall really happy as i was in a Jag XF prior and was getting 600km a tank so no complaints but would folks see a better fuel return by not using the active cruise control. I find myself that i am better able to maintain a decent speed more smoothly than cruise control when overtaking and planning an overtake as the cruise really kicks in after slowing for traffic ahead and then powers away again.  - Great system but yeah , thinking with out is better at the moment. 

 

[Moleman]

23 minutes ago, Brookied said:

Hi Guys, 

So after a few months and a number of filling the car from bottom to top I am curious on a couple of things that you fine folk may be able to help with. 

based in Ireland so figures are km's, fill up details and range below.  (rounded up the figures below!)

Range    Litres Added    l/100km         MPG
900               53.82                 5.9          48.13
870               53.79                 6.2          45.69
885               54.33                 6.1          46.01
896               55.16                  6.2         45.89
847               55.87                 6.6         42.82
833               53.00                6.4         44.40
870                56.43               6.5          43.55

So. during the middle of the fill ups i got into the habit of using the active cruise control  on the way to work and back from work,  its a duel carriageway so can cruise ok however my feeling was that it impacted the range a little.   My last fill up was NO cruise control used at all and the range increased again and hitting near 900km per tank.  Time between fill ups is between 2 and 3 weeks. overall really happy as i was in a Jag XF prior and was getting 600km a tank so no complaints but would folks see a better fuel return by not using the active cruise control. I find myself that i am better able to maintain a decent speed more smoothly than cruise control when overtaking and planning an overtake as the cruise really kicks in after slowing for traffic ahead and then powers away again.  - Great system but yeah , thinking with out is better at the moment. 

 

I do regular longer journeys and find the ACC better for mileage when on M or A roads with light traffic.

If busy, better to have control yourself as I find I anticipate better and use the hybrid system to best use.

[Las Palmas]

Cruise control function OK when no other cars on road.

When much traffic it is a rollercoaster with automatic braking and acceleration.

[Brookied]

thats what i am finding, if little to no traffic its ok, but when other cars are around its very erratic and cannot smoothly transition where i can anticipate better the power needed.  - nice to know i am not mad...  cheers 

[Herbie]

44 minutes ago, Brookied said:

thats what i am finding, if little to no traffic its ok, but when other cars are around its very erratic and cannot smoothly transition where i can anticipate better the power needed.  - nice to know i am not mad...  cheers 

Turn off ACC and just use 'normal' cruise control instead.

[Brookied]

good point @Herbie - might do that also. see what happens to the economy

 

[Illogan]

After a few years of driving our RX450, I have proven that cruise control is at it's most effective on 'flat' roads with a fairly consistent speed of 40mph+.

When on hilly roads, in busy traffic or when travelling under 30mph, I experience a better mpg with the cruise control turned off.

[KingHal]

Dedicated hypermilers recommend that you don’t use cruise control at all. As you’ve noted it tends to be very heavy footed when both accelerating and braking. 

You are also better placed to know when to manually “force” EV mode based on the road ahead - foot off the accelerator then feather it open to invoke EV. 

[ColinBarber]

There are two types of drivers, ones that are more economical than CC and others that aren't 🙂

Certainly it is possible to beat CC by being less aggressive on the accelerator, anticipating and reacting much sooner to congestion, allowing speed to bleed off slightly when going up hill and going slightly above the desired speed if the car accelerates down a hill rather than wasting energy by braking.

Equally I know people who drive as if the accelerator pedal is a switch and CC is much more economical for them, and smoother. 🤣

[PaulWhitt20]

I hardly ever use cruise control as I don't have the ACC, but I noticed when I did use old fashioned CC on a flat motorway at constant speed, the revs seemed to oscillate up and down over a period of 10 seconds or so. Possibly increasing revs to speed up to maintain speed, then overcompensating and then dropping down again to slow down. Not as efficient as driving without CC with a steady foot.

 

[Linas.P]

14 hours ago, Brookied said:

however my feeling was that it impacted the range a little.   

That is not much of the surprise really. The acceleration part is irrelevant, but braking is what impacts fuel consumption the most. Basically, you can drive fast and accelerate quite sharply, but looking ahead and avoiding unnecessary braking is what is most important for good economy. Cruise control is simply not smart enough to predict what will happen in front, so it will drive all the way up to the car in front and then brake, wasting a lot of fuel, whereas you can just let off accelerator way earlier and preserve a lot of fuel.

In short - there is no issue with CC or ACC, it is the issue with systems being unable to predict what will happen next and making wrong decisions.

On completely empty road I get same MPG with or without CC, I just use CC because I like to keep consistent pace. But if there is traffic then I can beat CC any time... although to be fair most of the time I choose not to do it.