I own a Passatt TDI estate ,highline 04 reg diesel which has now covered just over 72,000 on the clock.The car has has regular services at every prompt but I have noticed that the on board computer registering no more that 46/48 on the rolling clock ,flicking down the adverage miles is no more than 32/34 miles per hour on the clock.Most of my miles are spent motorway driving and my adverage speed hovers between 60/70 eack day.I have been to my local VW dealers who have had a full diagnostic and had the car for a whole day,they said the adverage mileage was 48.,they changed the air/oil filter.

I used to get a good 54 mph ,now i am left frustrated any ideas please

Thanks

Mark