megane 1.6 2003 MPG problem

[linux44]

i have recently noticed that MPG on my speedometer is showing some funny measure
for example when i reset the trip control the MPG is reset it
MPG start from 10 mile per gallon and if i drive in the city it drop down to 8 mile or even 6 mile per gallon(it is not lambo)
but if i go to highway it will go up again to like 23 mile or 24 mile in motorway
that is to low ,because renault megane is claiming that megane II should give at least 32 MPG ,urban driving and about 50MPG in highway

i also want to add that point that whenever i stop in the traffic down the MPG will drop for example when i reset it it is 10mpg then if i stop at traffic light it will drop to 7 mpg

i hope i have gave u enough information
can any one tell me what could be wrong with it?

[Danny140986]

not sure about the whats wrong but the mpg dropping when stopped at the lights is normal, as the computer takes into account the fuel used when the engine is running but the car is not moving

[myglaren]

Fill the tank, zero the odometer and drive it until the tank is nearly empty then refill.
From the odometer get the mileage covered and calculate the actual mpg from the amount of fuel used (ask for a VAT receipt it will have the fuel volume recorded).

This will give you a reasonably accurate figure for your average mpg. See if it tallies with the cars estimate of average mpg. My guess is that it will bear no resemblance, the cars computers can be hopelessly optimistic or pessimistic.
I'm almost pleased that mine doesn't work at all.

You really need to repeat this several times in succession and recalculate the grand average to get a realistic figure as there are so many variables that can skew the figures.

[Ross_K]

You have to fill the tank to the brim for the mpg reading to work properly.

Resetting the mpg on the computer if you've only got 1/2 or 3/4 of a tank is obviously not going to work. You don't say whether you're filling the tank or not so forgive me if I sound patronising...

It's normal for the mpg to drop when sitting in traffic - you're burning fuel and staying still, aren't you

[Xaccers]

Also the figures Renault give are not real world figures.

[ferkemall]

OK i drive a 1.6 Modus automatic the mpg went down to 25mpg around town i did some research and it runs a mapp sensor and the air temp unit they work together with the o2 to give read back to the ecu, but they are in the inlet manifold so i pulled them out and found them covered in oil ,used some electric circuit board cleaner and put them back looking at the problem of the pcv valve pumping the oil from the crankcase into the inlet i made an oil catch can out of a stainless steel vacuum flask and fitted it the engine now breathes clean air and the mpg went up to 33mpg around town from 25 also the emissions will be better there must be a lot of people driving out there doing less to the gallon and not even noticing it !

OOpps i forgot i also pulled the o2 and tested it with a gas torch and a multi meter it was in good shape !