Fuel Economy - Cruise Control

[wimorrison]

Driving to work this morning I did not use the cruise control, which I normally set at 75 (ish) and upon arriving at work I noticed that my consumption had improved by 0.1 MPG.

Not a lot, I hear you say but it made me recall the programme where Clarkson tried to drive from London to Edinburgh on a single tank and one of the things he said was that it was more effeicient to use manual speed control that automatic cruise control.

Has anyone experience of comparitive studies or personal experience to prove/disprove the theory?

[mu71rd]

i had been wondering this, and was discussing it with some friends on a trip this weekend.

I think if you are adamant you want to maintain a steady speed then cruise is best for MPG because it will choose the lowest rev/gear combo to maintain the exact speed.

But my friend told me he drove trying to keep a constant mpg on the instantaneous reading. ie - if he's going flat he aims (in his case) for 50mpg. If going down hill it means he speeds up, and uphill he slows down. Net speed is probably still the same, although it requires more concentration and does involve speed changes regularly.

he basically just keeps his foot in the same place the whole time, and let the car speed up or slow down according to the incline.

apparently gets much better mpg as a result.

[adambsmith]

A long time ago, we had a PT Cruiser Diesel which suffered horrendous MPG when using cruise - far better just using one's foot on that model.

[Mislovic]

i can't speak for all cars, but.. for the few cars which i had, it is more fuel efficient to manually adjust your throttle.

when I switch to instantenous fuel consumption, I found that most cars are still applying a bit of throttle, on roads which I would normally release the accelerator.

the difference is about 0.5 to 1ltr/100km, so, for the convenience, i would still use the cruise control for long distance driving.

[Bernard333]

Cruise control has been one function I have made sure I had on every car since 1995 because doing the high mileages I was clocking up through work the circulation in my right leg was becoming affected due to the long time spent resting on the accelerator so it became essential for me and I think without it I would not have been able to do the job . Fuel economy was also very important to me because the way my company reimbursed costs was based on mileage , on a typical 500 mile trip that meant I would either be in profit or making a loss which could be up to £20 so I would do everything possible to stay in profit and have kept exact records of fuel cosumption on every car I have driven . Cruise control uses more fuel in most driving situations my estimate is approx 3 to 4% but it depends on how the car is driven and the number of hills on the journey .

[wimorrison]

My 0.1mpg improvement became 0.2mpg improvement tonight when I drove home using the manual control rather than cruise control - quite a way to go to get the 3-4% suggested as possible, but I think that the argument is sound and I will use the mk1 human foot rather than the cruise control :)

[tem]

Cruise Control - Is a positive aid for me.

I do a lot of long distance driving and without the Cruise Control, I would find the journeys, exausting.

Just recently, returned from a round trip, from the North of Scotland, to Northern Italy (Sud Tyrol) and with Cruise Control (used, where ever possible), I averaged 39.8 mpg.

To gain a few extra mpg, with foot control (if this is possible), is not worth the effort and discomfort.

My views.

tem.

[Vecais]

Cruise Control is an essential driving aid for me to help avoid speeding tickets.

The Volvo Cruise Control is the best I have had for a couple of reasons, firstly the digital speed setting number is much more precise than the usual guess of a point on the speedo and secondly the speed control works down to about 30kph, great for passing roadworks or such.

Who cares about minor savings in fuel consumption. The value of one speeding ticket here will buy about 4-5 tank fills of fuel.

[watson-lfc]

I recently went down to donington park to watch a drifting event, 3 of us in the car and sat with cruise control on all the way there at around 80-85mph. used 3 quartes of tank to do around 200 mile!! On the way back i didn't use the cruise control and sat at about 90 and it used around half a tank. Thats a substantial difference isn't it?!

[XC60 N Yorks]

For what its worth, I have found the XC60 cruise control less fuel thirsty than any car I have previously owned, including "Er in doors" XTrail. But I agree foot control always wins.

If fuel economy is your thing, can I suggest keeping your XC60 very clean.

For the last 5 years I have done a routine weekend 150 mile round trip (same journey). While at my destination I have the opportunity to get the car hand washed for £6, and I always fill up on fuel as its much cheaper than where I live. A couple of months after I got the XC60 (had it 8 months now), I realised to my disbelief, that when I didn’t wash the car I used about 15-20% more fuel on the way home v when I have the car washed. Essentially the hand wash pays for itself on my journey home, and I have a shinny car for the start of the week.

Now I wash the car before any long journey.

[john h]

But my friend told me he drove trying to keep a constant mpg on the instantaneous reading. ie - if he's going flat he aims (in his case) for 50mpg. If going down hill it means he speeds up, and uphill he slows down. Net speed is probably still the same, although it requires more concentration and does involve speed changes regularly.

he basically just keeps his foot in the same place the whole time, and let the car speed up or slow down according to the incline.

apparently gets much better mpg as a result.

I think you might get better mpg, but I think it would be a road safety risk because of annoying other drivers (repeatedly overtaking, then slowing down again).

A good cruise control is very efficient. I had a Saab 9-5 Aero (2.3 petrol turbo 250bhp) and my overall fuel consumption, including a lot of early-morning motorway driving at 85mph on cruise, was 34.5mpg. Excellent for a 155mph exec car.

John

[r-designbob]

For what its worth, I have found the XC60 cruise control less fuel thirsty than any car I have previously owned, including "Er in doors" XTrail. But I agree foot control always wins.

If fuel economy is your thing, can I suggest keeping your XC60 very clean.

For the last 5 years I have done a routine weekend 150 mile round trip (same journey). While at my destination I have the opportunity to get the car hand washed for £6, and I always fill up on fuel as its much cheaper than where I live. A couple of months after I got the XC60 (had it 8 months now), I realised to my disbelief, that when I didn’t wash the car I used about 15-20% more fuel on the way home v when I have the car washed. Essentially the hand wash pays for itself on my journey home, and I have a shinny car for the start of the week.

Now I wash the car before any long journey.

Blimey, you've got heavy dirt where you live. :D

[wilbydoughboy]

One thing that I would have liked to have been included with the car would have been removable rear seats. I do the majority of my driving alone or with a passenger so if I could remove the rear seats I would. My previous car had easy removable seats and the weight of these adds to a good few mpg. With a clean and shiny car the air drag is much improved and having had many motorcycles I realise how air drag can add to mpg. Drivers leave their roof rails and racks on and these are small items but can add to much extra use of fuel.

[davidash]

I have found that the cruise control works particularly well on a route that is fairly flat. What it cannot do is anticipate hills and therefore goes from almost idle on the throttle to foot-flat as it encounters a hill. On balance I reckon the use of the cruise control comes out about even with your foot over an extended distance - never mind the relaxation factor!

[Dellsonic]

Yes the cruise control is great and precise with none of that "hunting" feeling. Getting 33 mpg on and XC60 D5 AWD at 80.

Dell

[wimorrison]

so it seems the consensus is that you do get better mileage with the cruise control. I agree that it is a useful function on longer journeys, though I find that I sometimes drive using the foot to stop the boredom :)

The thing I really miss from a Merc I had at one point is the speed limiter - brilliant for saving speeding tickets, you set the max speed and off you went, impossible to go above the limit set.

I am sure someone will say that it was unsafe, with the story that you need to accelerate to get out of trouble, well you still could, but you couldn't break the speed limit :)

[tem]

so it seems the consensus is that you do get better mileage with the cruise control. I agree that it is a useful function on longer journeys, though I find that I sometimes drive using the foot to stop the boredom :)

The thing I really miss from a Merc I had at one point is the speed limiter - brilliant for saving speeding tickets, you set the max speed and off you went, impossible to go above the limit set.

I am sure someone will say that it was unsafe, with the story that you need to accelerate to get out of trouble, well you still could, but you couldn't break the speed limit :)

Para 1 - Waggle your toes, stretch your legs, message your bum - no boredom.

Para 3 - Slight contradiction here, with Para 2.
Had the Merc, with the speed limiter.
With the speed limiter set to 60 mph, how can someone exceed this, to get out of trouble?

Or am I missing something?

tem.

[wimorrison]

Para 1 - Waggle your toes, stretch your legs, message your bum - no boredom.

Para 3 - Slight contradiction here, with Para 2.
Had the Merc, with the speed limiter.
With the speed limiter set to 60 mph, how can someone exceed this, to get out of trouble?

Or am I missing something?

tem.

yep, your missing something

[tem]

yep, your missing something

What?

tem.

[Bernard333]

so it seems the consensus is that you do get better mileage with the cruise control. :)

No definitely not , for someone like myself who would deliberately attempt to get a very high mpg on a long journey I wouldnt use it in that situation . Problem for me is that its become physically very difficult for me to manage without it so I am in favour of cruise control albeit that I know I am paying a small price in extra fuel used for its use .

[wimorrison]

No definitely not , for someone like myself who would deliberately attempt to get a very high mpg on a long journey I wouldnt use it in that situation . Problem for me is that its become physically very difficult for me to manage without it so I am in favour of cruise control albeit that I know I am paying a small price in extra fuel used for its use .

Arrggh, you spotted the error in my message - it should have read

so it seems the consensus is that you do get better mileage without the cruise control

my apologies and thanks for pointing this out :)

[Aidan Bell]

I've been having similar thoughts regarding air-conditioning, and how much saving there'd be in not using that too (Volvo recommend keeping air-conditioning on at all times, and during the two weeks I've now owned my XC60 I have done so). But I must confess my attitude to both cruise control and air conditioning is quite simple; don't spend £20,000-30,000 on a car and then drive it like a teenager trying to save a few quid! As I'm sure is likely to be the case with most of us on this forum, I've put a lot of money and effort into my car and I don't intend to jeopardise that for the sake of a small saving in fuel.

One thing I would say about cruise control is that it is a double-edged sword. On the one hand adaptive cruise control in the XC60 is nothing short of astounding. Apart from steering the car practically drives for you! But the downside of that is of course complacency - which can be highly dangerous - as well as eventually a feeling of "who's driving this car anyway?". I've had mine for two weeks now and have already realised that superb though the cruise control is, controlling one's own cruise in the XC60 is actually a very enjoyable experience!

[Daleman]

I've been having similar thoughts regarding air-conditioning, and how much saving there'd be in not using that too (Volvo recommend keeping air-conditioning on at all times, and during the two weeks I've now owned my XC60 I have done so). But I must confess my attitude to both cruise control and air conditioning is quite simple; don't spend £20,000-30,000 on a car and then drive it like a teenager trying to save a few quid!

You must have a different type of teenager down south they don’t drive trying to save a few quid up here its tyres squealing on take off, maximum in all the gears all the way with the noisiest exhaust they can lay their hands on with no thought for economy!

[Aidan Bell]

You must have a different type of teenager down south they don’t drive trying to save a few quid up here its tyres squealing on take off, maximum in all the gears all the way with the noisiest exhaust they can lay their hands on with no thought for economy!
Yeah, OK, I just wanted an example of a financially poorer demographic, but probably could have done better than teenagers!

[Daleman]

Yeah, OK, I just wanted an example of a financially poorer demographic, but probably could have done better than teenagers!

Yeah OK understand perfectly what you mean !

[wimorrison]

Why is it assumed that when you start to discuss fuel economy you are assumed to be in the 'financially poorer demographic' and that you are not worthy of owning a XC60?

If fuel economy was of not interest to those on the forum, or elsewhere, why have has Volvo produced a range of engines and transmissions from the frugal 2wd Drive models through to the powerful 4wd engines.

Surely the only reason would buy a different engine is because of the economics of the less powerful, more fuel efficient engine which when allied to 2wd provides a larger MPG.

Those of us with the d5 AWD vehicles can afford the fuel, we are not in the financially poorer demographic, but that does not mean that we should not be interested in getting the maximum return for the fuel that we purchase - in fact that argument applies to all, whether it is with the fuel efficient engines or the beasts delivering larger outputs.

A corollary to this argument is why consider an XC vehicle then disable it by purchasing it with 2wd - that could more easily be seen as someone from the financially poorer demographic trying to pretend that they are in the financially healthier demographic.

[Aidan Bell]

Why is it assumed that when you start to discuss fuel economy you are assumed to be in the 'financially poorer demographic' and that you are not worthy of owning a XC60?

I wasn't making that assumption at all, quite the reverse in fact. My "assumption", if any, was that those who can afford an XC60 are not likely to be those who want to quibble over a few pounds on fuel expense to the detriment of the performance of their expensive new car. However I think we are basically singing from the same hymn book; if you want to save money by a Fiesta!