MPG: Fuel Economy and cruise control

richierich · 26th May 2006, 07:59

I have been struggling to get my fuel economy above 45mpg on this tank full, seems that I can do well round town but once on the motorway with the CC on the mpg drops to around 40, even travelling on the flat, after 10 - 15 minutes of M'way driving it gets better, also noticed yesterday on the way back from work I had to turn off the cruise control cos some idiot pulled out in front, but when I got back up to speed and I turned it back on the the fuel economy bar chart sat at 45mpg for 5 - 6 seconds, dropped all the way to zero, sat there for a while and I then managed to get 50-55mpg all the way home, even up slight inclines. Seems to be a bit random how much fuel the cruise control uses.

Is there a knack to getting good mpg with the CC on?

Pottsy · 26th May 2006, 22:15

I get this exact behaviour - here's my theory on two parts:

The CC holds a constant speed, so it will tend to move the throttle a lot to maintain the constant speed. On a turbo car this makes it come off and on boost a lot, which is not that efficient. You're probably better off turning off the cc and driving without it...

BUT

I have noticed that sometimes fuel economy is poor (42 ish compared to 50 ish). My own theory is that the car needs to recalibrate itself for new environmental conditions (temp, pressure etc). I have found that one full throttle blast allows it to recalibrate, and the economy jumps up. Try it, once the engine has warmed up fully (a few minutes after the water temperature has come up to normal).

Hartside · 26th May 2006, 22:39

Pottsy, is that a full throttle blast with the car in neutral, or a full throttle blast in a gear.

Pottsy · 26th May 2006, 23:10

er, in gear! Just to give it full load for a few seconds - allows it to calibrate for the atmospheric conditions.

richierich · 29th May 2006, 10:31

Did quite a long run yesterday and Saturday, averaged around 50mpg on the motorway, I did notice that after a good pull uphill with the CC on the economy after was a lot better, slowly getting used to it, although have to have the fuel economy bar chart on all the time.

26th May 2006, 07:59	#1 (permalink)
richierich Smell My Cheese! Rocketship door handle Join Date: 17th May 2006 Location: Bicester, Oxfordshire Posts: 1,843 Thanks: 0 Thanked 0 Times in 0 Posts	Fuel Economy and cruise control I have been struggling to get my fuel economy above 45mpg on this tank full, seems that I can do well round town but once on the motorway with the CC on the mpg drops to around 40, even travelling on the flat, after 10 - 15 minutes of M'way driving it gets better, also noticed yesterday on the way back from work I had to turn off the cruise control cos some idiot pulled out in front, but when I got back up to speed and I turned it back on the the fuel economy bar chart sat at 45mpg for 5 - 6 seconds, dropped all the way to zero, sat there for a while and I then managed to get 50-55mpg all the way home, even up slight inclines. Seems to be a bit random how much fuel the cruise control uses. Is there a knack to getting good mpg with the CC on?

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This thread is about: Fuel Economy and cruise control, it's in Engines and Transmission at the Honda Civic forum Civinfo; I have been struggling to get my fuel economy above 45mpg on this tank full, seems that I can do well round town but once ...

26th May 2006, 22:15	#2 (permalink)
Pottsy Administrator Civinfo guru Join Date: 10th April 2006 Location: Leics Posts: 4,643 Thanks: 3 Thanked 49 Times in 23 Posts	I get this exact behaviour - here's my theory on two parts: The CC holds a constant speed, so it will tend to move the throttle a lot to maintain the constant speed. On a turbo car this makes it come off and on boost a lot, which is not that efficient. You're probably better off turning off the cc and driving without it... BUT I have noticed that sometimes fuel economy is poor (42 ish compared to 50 ish). My own theory is that the car needs to recalibrate itself for new environmental conditions (temp, pressure etc). I have found that one full throttle blast allows it to recalibrate, and the economy jumps up. Try it, once the engine has warmed up fully (a few minutes after the water temperature has come up to normal).

26th May 2006, 22:39	#3 (permalink)
Hartside Supporter Magic Rear Seat Join Date: 4th May 2006 Location: Northumberland Posts: 547 Thanks: 0 Thanked 0 Times in 0 Posts	Pottsy, is that a full throttle blast with the car in neutral, or a full throttle blast in a gear.

26th May 2006, 23:10	#4 (permalink)
Pottsy Administrator Civinfo guru Join Date: 10th April 2006 Location: Leics Posts: 4,643 Thanks: 3 Thanked 49 Times in 23 Posts	er, in gear! Just to give it full load for a few seconds - allows it to calibrate for the atmospheric conditions.

29th May 2006, 10:31	#5 (permalink)
richierich Smell My Cheese! Rocketship door handle Join Date: 17th May 2006 Location: Bicester, Oxfordshire Posts: 1,843 Thanks: 0 Thanked 0 Times in 0 Posts	Did quite a long run yesterday and Saturday, averaged around 50mpg on the motorway, I did notice that after a good pull uphill with the CC on the economy after was a lot better, slowly getting used to it, although have to have the fuel economy bar chart on all the time.