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Smell My Cheese!
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Discussion Starter #1
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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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).
 

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

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Smell My Cheese!
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Discussion Starter #5
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.
 

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Sorry to come up with his old thread but i thought i'd be a good boy and get on with previous threads instead of making a new one.

My car uses a LOT more fuel when the cruise control is on then when working the pedal. Even when going downhill the car uses fuel when cruise control is on, this can be up to 4 L / 100 km! Even when going at a steady peace the CC makes the car far more thirsty. I did try to give it some good blasts when warmed but it still remained (but i drive the petrol).
So now i wonder if the CC and i-VTEC system are working well together or if there is even some sort of interaction between the two. Putting CC on, i would expect for the i-VTEC to be working almost non stop (driving @ constant speed just under 3000 rpm so slight throttle needed) except when going uphill. No major issue but this has resulted in me using the CC a lot less then before!
Just had to get this of my chest :)
 
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