hi im driving a mk4 golf 1.9 tdi match pd100 which was 100bhp 240torque now re-maped to 130bhp 320torque + a gain of up 10% extra fuel by powertune
im getting 41 round town and 45 on the motorway aslong as i do 70-90mph in 5th at 2500rpms-3000rpms this is short journeys so guessing id probably get more
but i must say im getting this figure by running on 16'' montreal alloys tyre size 205/55/16
and before this i had some brand new 18'' rs8's alloys tyre size 225/35/18 and was losing alot as figures use to show 36 37 round town and 40.5 motorway
parkers book quotes 45mpg for my standard pd100 with 5 speed gearbox
55mpg for the gti tdi pd130/150 models as these are fitted with a 6 speed gearbox
they get this figure by running on standard stuff i.e the gti 15'' alloys with 195/75/15 tyres plus without mud flaps fitted. as fitting mudflaps and wide tyres theres road drag/grip to consider here.think about it 195 tyres all round then jumping to 225 tyres is going to change more than traction
p.s try reseting the trip computer as this might give a better reading as i find this helps