Using cruise control more economical or not ?

I’m not convinced it is, it seems to over rev when it doesn’t need to when going on slight incline etc

Thoughts ?

Probably depends on the driver, the car and the road.

Yes, or no.

Depends on a multitude of things.

Will make a negligible difference either way.

Depends.

Are you normally one of those drivers who thunder past at 90, who you then pass five miles down the road doing 60, who then thunder past at 90 and repeat?

A bit less if I’m driving carefully I reckon – when driving manually I’ll ease off a bit on the hills where the cruise floors it.

jam bo – Member

Depends.

Are you normally one of those drivers who thunder past at 90, who you then pass five miles down the road doing 60, who then thunder past at 90 and repeat?

What the **** is that about anyway?

Its not the cruise control that makes a massive difference to fuel economy per se. Yes an amazing driver can beat cruise control for fuel economy but its hardly anything.

Its the lack of forward planning, awareness and basic driving skills both on or off cruise control that effects fuel economy. Lets face it, cruise is mainly for motorways. How many times do you brake and lose momentum on the motorway? How many times do you look to change lanes to overtake and find you have to slow down because a faster car is approaching in the outside lane? How many times do you have to slow down because a car/lorry in inside lane is pulling out. You haven’t been paying attention enough and could have just glided into the next lane so no party had to brake.

There are so many things that effect fuel economy and cruise isn’t a patch on most of the causes. I used to do a 120mls round commute to work for 4.5yrs. To keep it interesting I used to challenge myself to do the entire motorway section without ever having to touch the brakes. I now drive with an awareness of cars much much further away. I watch cars approaching wagons at speed and try to allow space for them to pull out even if they haven’t indicated. Wgaons thank you because you are expecting them to start indicating because they have approached a wagon in front and have already checked that you are ok to change lane to move outside.

Or you could just leave the cruise control on. Hit the brakes when you come up behind a slower car in the middle lane and join the rest of the people who cant get good fuel economy

Probably not, I spend 95% of my driving time on cruise control. It will still try and keep the set speed on slight inclines, but I find the odd time I drive without CC set on small inclines I will find myself either taking it a bit easier up the incline or I’m not pressing the gas any more than I was so the speed drops slightly……sticking my wet finger in the air I’d guess that those sort of times I’m using less fuel.

The other question is, will I ever stop mixing it up with the stereo volume control….probably not!

You don’t need to be an amazing driver to beat it, just don’t floor it up hills. Having said that, most of the time I set the cruise controll to 69mph on the GPS, whereas driving normaly I’d be more likely to be 62-66mph on the GPS (i.e. <70 on the speedo) as I’m allowing the narutal oscilations in speed to be under the limit 90% of the time, whereas I’d trust the cruise contorll to keep it +/-1mph all the time, so it probably ends up a higher average speed. 5% more speed is a probably more than 5% more fuel.

Although I guess you couln’t beat the newer radar cruise controlls which in theroy should let you slipstream anything infront.

i drove a car recently with adaptive cruise control.
and haptic feedback through the steering wheel if you got too close to the white lines.
and warnings if someone was in your blind spot.

gave me plenty of time to catch up on my email 8)

I’ve compared cruise control to manual going to and from Spain whilst travelling on the toll roads. No matter how careful I am I have never been able to beat the cruise control which will always give me that extra 1-2mpg. I think the key is the cruise control detects the start of a decent quicker than I do and starts to ease off sooner. It’s also a lot less tiring using cruise control.

My experience of cruise control is that on the same journey, regardless of how carefully I drive, the cruise control will always be more economical. I had a Megane hire car which would get around 79mpg on cruise from Sheffield to Leeds and 71mpg without it. Without cruise it was comparable to my normal car.

Mainly what Litle Hobo said. My current Passat doesn’t have it but my last one did (same engine etc) & I’m getting miles better mpg in this than the previous one.
The only real time I appreciated it was when we drove from Montpellier to Calais in one sitting, just stuck it on 80mph & only slowed for the toll booths.

…detects the start of a decent quicker than I do and starts to ease off sooner. It’s also a lot less tiring using cruise control.

Also this – most people tend to initially allow the car to speed up on a descent, cruise control immediately backs off to keep the speed constant.

If you search hard enough OP there’s an internet experiment whereby the results for your car are that its most economical when driven in “manually” with the relevant care and consideration described above.

I used to be able to ‘beat’ the cruise control on my Golf comfortably. Wasn’t really the point of it I guess.

More economical on the muscles in yer leg.

Yes on open flat-ish roads. No on windy ones.

It’s because accelerating uses a disproportionate extra amount of fuel – so if you let your speed creep up then slow down again it uses quite a bit more fuel. If you ease down on the throttle ever so slightly, so it’s not even noticeable, the instant mpg reading will still plummet.

Or you could just leave the cruise control on. Hit the brakes when you come up behind a slower car in the middle lane

You can still use cruise and drive as you describe. Just disengage it in good time.

What I find to be more effective than using/not using cruise control is simply switching off air con and even the heated rear mirrors (my Audi mirror controls either set it to adjust left/right or if it is in the centre it is on heated) so I set it to ‘adjust’ one side and not heat. It really does seem to make a big difference.

Just disengage it in good time.

or with adaptive cruise control it slows down and speeds up for you. I used these recently in a Golf hire car the M1 and drove for 40 miles without touching anything but the steering wheel and indicators – cruise control set to 80. quite remarkable.

I’ve never been able to identify if AC makes a difference or not – so I conclude that it makes a difference so small to be masked by other factors.

My car can comfortably get about an additional 4mpg if I switch off all the periphery.

Presumably you can then just sit in the middle lane in order to avoid too much steering input, and let it slow you down to sit behind any cars in front of you, but speed up as soon as it’s clear?

I think it does, bu then again I switch it on and then use it rather than the accelerator and brake, so probably spend less time accelerating.

Not.

A driver can see the contour of the road ahead, the cruise control can’t. As such, YOU can freewheel a little faster down the hill, thereby using less energy to climb the other side of it.

If I set my cruise to 70 on a 240 mile journey from home to Leeds, it’ll average between 31-33 depending upon traffic and weather. If I drive the same journey without, and allow my speed to vary between 55 and 90, the average MPG over the same journey is 38-40mpg. The journey time increases from ~3.5 hours to ~4.

Daffy – you are not comparing the same type of journey then are you if you drop to 50 🙄

aracer >> Presumably you can then just sit in the middle lane in order to avoid too much steering input, and let it slow you down to sit behind any cars in front of you, but speed up as soon as it’s clear?

probably. I just overtook though as I wasn’t sure how much it would slow down and/ or stop if it needed to.

A driver can see the contour of the road ahead, the cruise control can’t. As such, YOU can freewheel a little faster down the hill, thereby using less energy to climb the other side of it.

This isn’t true when the laws of mechanical drag and aero effiency are applied. There’s a less greater negative offset and even a loss dependant on the speed you achieve over the constant – depending on its speed.

FunkyDunc – Member
Daffy – you are not comparing the same type of journey then are you if you drop to 50

Congratulations, you managed to read (incorrectly) one figure from my post, but completely miss the point.

I genuinely hope you aren’t in charge of anything which requires attention to detail.

I’ll let you off then.

This isn’t true when the laws of mechanical drag and aero effiency are applied. There’s a less greater negative offset and even a loss dependant on the speed you achieve over the constant – depending on its speed.

🙄 mechanical losses in the driveline and combustion inefficiency in the engine are substantially greater loss factors (>60% of losses) at these speeds than drag (<10%).

Gravitational acceleration on anything over a very shallow gradient will quickly exceed the Aero and Rolling resistance losses.

and allow my speed to vary between 55 and 90

That would be too great of a variation in speed for me.

It’s most efficient to speed up resonably quickly then coast to a near standstill. But that’s not considered acceptable for reasons of traffic flow. I would consider varying between 50 and 90 similarly unacceptable.

If you are attempting to keep a constant speed, and the road is relatively open and not windy (as I said originally) then cruise will be more efficient. If you are going to dick about then it won’t.

Gravitational acceleration on anything over a very shallow gradient will quickly exceed the Aero and Rolling resistance losses.

Eh?

You mean that converting your gravitational potential energy into kinetic energy is the best place for it – since the only other option is heat in the brakes. UNLESS you are driving a hybrid so you can opt to put it into the battery instead…

More economical on the muscles in yer leg.

more economical on your licence too if you go through any “average speed” controlled areas.

There is a halfway house – driving using the cruise control, not just setting it and leaving it on until you have to brake. I switch mine on and off and use the accelerate and decelerate buttons all the time when the road isn’t empty or flat.

That’s not really using the cruise though, chief – I have to admit it is what I tend to do as well, even occasionally going so far as to drop the speed a couple of clicks on a long uphill (one obvious place on the M40 heading towards London I do this).

aracer >> I’ll let you off then.

I thought I sensed some sarcasm in your post 😉

I can beat cruise control on a motorway. Not by much, 2mpg maybe, but I can.
IMO it’s because I don’t try and keep the same speed all the time, I’ll slow slightly up hills and speed up slightly going down for instance. When I was doing the same journey twice a week there was a noticeable increase in fuel consumption when I had the CC fitted.
I can point it out on the graph if anyones that sad/bored/interested…? 🙂

Daffy – go on please explain, I am obviously thickerer than you

I use cruise a lot, both on city streets with a 20 or 30 limit, and on the motorways. Drive very smoothly on the motorway with early lane changes and only braking if something has gone wrong – ie the intention is to not brake.

Katie doesn’t like cruise and her speed tends to vary much more with far more touching of the brakes. Her peak speed is higher than I set cruise to but she seems to nearly always get slightly better economy. I’m sure it’s not like for like driving – I probably accelerate a bit harder when the cruise is off but on a long journey that’s mostly motorway I’d not have expected that to over-ride.