mpg with cruise control

andre372 · 29th May 2014, 23:19

Has anyone noticed or even measured the difference in mpg when using cruise control and when not?

The reason I ask is that a bloke in the local electronics store I visited rather often when doing wiring for my cruise control told me that with his BMW fuel consumption increased by 3 litres for a 120 km (~75 miles) highway trip when driving with cruise control enabled. I can't remember if he said how he measured it, but I did ask if the the conditions where equal. Same road (back and forth), same speed, climate off etc. Obviously even brim to brim measurements aren't very accurate with such short journeys and much depends on petrol pump and if car is level, but such rise just doesn't seem logical.

Has anyone noticed an increase/decrease in mpg with cruise control?

clf · 30th May 2014, 00:19

Quote:

Originally Posted by andre372

Has anyone noticed or even measured the difference in mpg when using cruise control and when not?

The reason I ask is that a bloke in the local electronics store I visited rather often when doing wiring for my cruise control told me that with his BMW fuel consumption increased by 3 litres for a 120 km (~75 miles) highway trip when driving with cruise control enabled. I can't remember if he said how he measured it, but I did ask if the the conditions where equal. Same road (back and forth), same speed, climate off etc. Obviously even brim to brim measurements aren't very accurate with such short journeys and much depends on petrol pump and if car is level, but such rise just doesn't seem logical.

Has anyone noticed an increase/decrease in mpg with cruise control?

My right foot is always lighter than the ECU............ well in my own cars it has been. My Jag XType, had a brilliant cruise, with no feeling of the power coming on or off. But the economy seemed to be lower. The ZT is the same. My father's old Megane cruise, was better at economy by about the same as mine was worse.

My test was a basic non (very non!) scientific test. As part of my commute, there is a short motorway stretch of about 4 miles. Each time they were 'tested', I was going to work, with a little traffic, but not enough to restrict my speed should I have wanted to drive at 70mph.

The reason why I 'tested' was to see if I was better or the car was better.

I would reset the computer as I went into top gear, 5th on the Jag, 6th on the Megane and my ZT is auto, so I cruised. All speeds were in and around 55-60mph. But if I was at 55mph with the cruise, I would try to keep 55 without. (or 60 with, and 60 without).

The Jag driving manually, would do around 62mpg, and 58 with cruise.

The Megane manually was 65mpg, and 66 with cruise (but you felt the speed drop off and pick up noticeably)

The ZT manually, was 50mpg and 44 with cruise.

As I said, these were not scientific, nor particularly indicative of true mpg. They were done one day after another, with weather I think similar, there was no account for ambient temps or engine temperatures. It was merely a guide because I noticed the Jag economy seemed to fall slightly when I played with the cruise. I used the motorway section, because it was the only part of my regular journey I could call a constant ie no traffic lights, roundabouts etc

I am not a fan of cruise unless I am on holiday abroad in a car.

I didnt know my father was watching his economy over the previous 4 or 5 months, when I borrowed his car

oops

Jay · 30th May 2014, 07:45

Funny you say that andre372 as when I rarely use cruse control but when I come to a hill, I notice an increase (surge) of power from the car on cruise that I do not feel when I have my foot on the gas peddle going up same said hill.
So yes it would make sense to me if it uses more fuel on cruise in certain conditions.

klarzy · 30th May 2014, 08:41

Quote:

Originally Posted by Jay

Funny you say that andre372 as when I rarely use cruse control but when I come to a hill, I notice an increase (surge) of power from the car on cruise that I do not feel when I have my foot on the gas peddle going up same said hill.
So yes it would make sense to me if it uses more fuel on cruise in certain conditions.

Does the cruise not work on torque output instead of rolling speed when it comes to climbing?, as the torque increases it would tend to up revs or shift down to peek the same speed on the road... it stands to reason you need more energy to defeat gravity than you do on the flat...

KWIL · 30th May 2014, 08:54

I have noticed that a large number of drivers slow down visibly (compared with me on KV6 Cruise Control) when climbing hills, they then "notice" that they are slower at the top and accelerate, quite often passing me when I am still maintaining 70mph. Overall I would not expect significant differences of consumption in these instances.

coab · 30th May 2014, 09:07

I use less fuel on cruise about 2 mpg but with all the idiots who just pull out infront of you on motorways and don't speed up I find unless its a quiet road its a non starter switching it on and off, speeding up to pass the offending car etc. When switching it on and using it it made me feel whoosy at first with the pick up and slow down motions to maintain speed!

berkshirelad · 30th May 2014, 09:14

My experience is an increase in mpg by using cruise on long trips.

CC is better at maintaining a set speed than my right foot; it makes small efficient adjustments rather than noticing that the speed has dropped by a few mph and accelerating back up (and usually fractionally past) the target speed.

Where CC can be less fuel efficient is uphill. Most drivers allow speed to drop off when climbing a hill (and allow over-speed on downhill stretches in undulating roads). CC will keep the speed constant.

Loads of use in the USA has proven to me that CC is more economical overall (and licence preserving)

My main bugbear with CC is those who pass, pull in and then slow down - requiring me to brake (and unlock the CC) or overtake them.

Jay · 30th May 2014, 09:32

Quote:

Originally Posted by klarzy

Does the cruise not work on torque output instead of rolling speed when it comes to climbing?, as the torque increases it would tend to up revs or shift down to peek the same speed on the road... it stands to reason you need more energy to defeat gravity than you do on the flat...

I agree Peter but instead of a smooth climb without cruise, with cruise the power kicks in like an automatic down shifting

snorbitz · 30th May 2014, 09:39

Quote:

Originally Posted by KWIL

I have noticed that a large number of drivers slow down visibly (compared with me on KV6 Cruise Control) when climbing hills, they then "notice" that they are slower at the top and accelerate, quite often passing me when I am still maintaining 70mph. Overall I would not expect significant differences of consumption in these instances.

I have also noticed most driver slow down when going around a slight bend on the motorway. My cruise keeps the car going at the same speed I set it so I usually have to disengage the cruise or move lanes while the driver in front makes the adjustment in speed.
As for a difference in mpg, I haven't noticed any difference yet, but I haven't used it enough to show any real difference.

wesley · 30th May 2014, 10:24

i use cruse control quite a lot when we travel down to hayle to see my wifes family. i cant say ive noticed any difference in fule consumption when using it.

when going up hills the gearbox changes down a gear at about the same time in cruse as it would if i had my foot on the pedal.

29th May 2014, 23:19	#1
andre372 Gets stuck in 2001 Rover 75 Tourer 2.0 CDT manual Royal Blue (JFM) Join Date: Dec 2012 Location: Viljandi, Estonia Posts: 855 Thanks: 233 Thanked 98 Times in 87 Posts	mpg with cruise control Has anyone noticed or even measured the difference in mpg when using cruise control and when not? The reason I ask is that a bloke in the local electronics store I visited rather often when doing wiring for my cruise control told me that with his BMW fuel consumption increased by 3 litres for a 120 km (~75 miles) highway trip when driving with cruise control enabled. I can't remember if he said how he measured it, but I did ask if the the conditions where equal. Same road (back and forth), same speed, climate off etc. Obviously even brim to brim measurements aren't very accurate with such short journeys and much depends on petrol pump and if car is level, but such rise just doesn't seem logical. Has anyone noticed an increase/decrease in mpg with cruise control?

30th May 2014, 07:45	#3
Jay This is my second home Small....Far away Join Date: Feb 2010 Location: Norwich Posts: 9,473 Thanks: 2,707 Thanked 2,060 Times in 1,194 Posts	Funny you say that andre372 as when I rarely use cruse control but when I come to a hill, I notice an increase (surge) of power from the car on cruise that I do not feel when I have my foot on the gas peddle going up same said hill. So yes it would make sense to me if it uses more fuel on cruise in certain conditions. __________________ ~Karma will help or hinder you. Therefore look positive for this day~

30th May 2014, 08:54	#5
KWIL Precise Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013 Location: Fleet Posts: 2,954 Thanks: 630 Thanked 617 Times in 480 Posts	I have noticed that a large number of drivers slow down visibly (compared with me on KV6 Cruise Control) when climbing hills, they then "notice" that they are slower at the top and accelerate, quite often passing me when I am still maintaining 70mph. Overall I would not expect significant differences of consumption in these instances.

30th May 2014, 09:07	#6
coab This is my second home 2007 57 GOLF GTi EDITION 30 DSG Join Date: Nov 2011 Location: Newport Shropshire and Coventry. Posts: 5,138 Thanks: 2,424 Thanked 1,452 Times in 852 Posts	I use less fuel on cruise about 2 mpg but with all the idiots who just pull out infront of you on motorways and don't speed up I find unless its a quiet road its a non starter switching it on and off, speeding up to pass the offending car etc. When switching it on and using it it made me feel whoosy at first with the pick up and slow down motions to maintain speed!

30th May 2014, 09:14	#7
berkshirelad Gets stuck in Rover 75 Tourer Connoisseur SE Join Date: Jan 2012 Location: Newbury Posts: 836 Thanks: 9 Thanked 101 Times in 91 Posts	My experience is an increase in mpg by using cruise on long trips. CC is better at maintaining a set speed than my right foot; it makes small efficient adjustments rather than noticing that the speed has dropped by a few mph and accelerating back up (and usually fractionally past) the target speed. Where CC can be less fuel efficient is uphill. Most drivers allow speed to drop off when climbing a hill (and allow over-speed on downhill stretches in undulating roads). CC will keep the speed constant. Loads of use in the USA has proven to me that CC is more economical overall (and licence preserving) My main bugbear with CC is those who pass, pull in and then slow down - requiring me to brake (and unlock the CC) or overtake them.

30th May 2014, 10:24	#10
wesley Loves to post 75 saloon Join Date: Jan 2011 Location: Nuneaton Posts: 401 Thanks: 292 Thanked 61 Times in 58 Posts	i use cruse control quite a lot when we travel down to hayle to see my wifes family. i cant say ive noticed any difference in fule consumption when using it. when going up hills the gearbox changes down a gear at about the same time in cruse as it would if i had my foot on the pedal.