2004 Renault Scenic miles per gallon

check the air filter 1stto see if it is blocked, a blocked or dirty filter will cut down the volume of air entering the engine therefore using more fuel

Thanks Moley1956
But when i first noticed the problem when i bought the car i got my mechanic to give it a full service.he said all the old fillters were blocked solid so thought this was the problem.put all new fillters in about Sept 2009 but did not solve problem.anymore ideas please

Thanks Moley 56. Had complete service done when bought car mechanic said all filters were blocked so new ones put on. Made no difference to fuel consumption. Any more ideas?
Thanks

hi,does the engine have high revs at idle for longer than normal,if so poss the cold start device is staying on to long, this injects more fuel when cold less when warm, if cold start device thinks engine is cold it will inject too much fuel giving high consumption.