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sathound
18-09-2007, 09:54 AM
I have been meaning to ask if the "live-1" rather than "average-2" mpg readout is so erratic as to be useless on other cars?

My live mpg literally cycles between an approx minimum of 11mpg under acceleration to a maximum of 109mpg and when you take your foot off immediately shows ----.

I only therefore ever use the average display which I reset when filling up.

Is this normal or is my car faulty?

mluton
18-09-2007, 10:29 AM
I only use the average to, mine acts the same.

mac500
18-09-2007, 11:44 AM
No. Apparently that is how it works. Mine does exactly the same. If yours is faulty, they are all faulty. You are supposed to be able to use the instantaneous mpg figures to adjust your driving technique for maximum fuel economy but the readings are so erratic as to make them useless for that purpose or any other purpose. I also stick with the average mpg setting.
cheers

Quatrelle
18-09-2007, 04:27 PM
No. Apparently that is how it works. Mine does exactly the same. If yours is faulty, they are all faulty. You are supposed to be able to use the instantaneous mpg figures to adjust your driving technique for maximum fuel economy but the readings are so erratic as to make them useless for that purpose or any other purpose. I also stick with the average mpg setting.
cheers
Same here. To my mind it's just a useless distraction.

Santana
18-09-2007, 07:02 PM
Actually I like the instantaneous mpg readout. I wouldn't call it erratic. With mine it responds just as I'd expect to pressing the throttle or lifting off, going uphill, down hill etc. As I haven't had the car for very long - 6 months - I find it useful. I can see instantly what type of driving produces what type of mpg.

carl s
18-09-2007, 10:33 PM
To be honest I find the most useful readout the one that tells you how many miles you've got left in a tank, the rest are all a bit gimmicky

angus
20-09-2007, 01:09 PM
Normally I find the reading superflouous, but it is very useful when towing a caravan.

very often you can be on a road at a given speed with the car rolling along easily, only to find that changing down and seemingly revving harder actually improves the consumption.

I did this last week on a 280 mile tow and overall consumption was 1.8 mpg better than usual.

I wouldn`t drive like that solo, when the reading is a distraction unless you get bored and need to play keep it above 50/60 whatever on deserted roads.

ngoodger
20-09-2007, 02:33 PM
Hi

For your info, apparently the display shows --- because when you freeroll while still in gear i.e. do not press the accelerator while car decelerates, the engine does not use any fuel. If you were to take the car out of gear you and freeroll you actually use fuel to keep the engine ticking over.

Don;t quite understand the technicalities of how this works but saw it on Top Gear when they drove an Audi A8 on a return journey from London to Edinburgh on a single tank of fuel.

NGoodger

carl s
20-09-2007, 10:02 PM
Hi

For your info, apparently the display shows --- because when you freeroll while still in gear i.e. do not press the accelerator while car decelerates, the engine does not use any fuel. If you were to take the car out of gear you and freeroll you actually use fuel to keep the engine ticking over.

Don;t quite understand the technicalities of how this works but saw it on Top Gear when they drove an Audi A8 on a return journey from London to Edinburgh on a single tank of fuel.

NGoodger


That's because on deceleration the engine management cuts the supply of fuel because the transmission keeps it revolving, whereas on tickover the engine needs fuel to keep itself running. It's a clever little bi-product of modern fuel injected systems, older cars will happily chuck fuel in when it's not needed.