Originally Posted by CHG
Thanks for your advice guys - in reply to Ti Rich, I took my 318 on a long trip down to Bath (220 Miles) and with cruise control set at 80 all the way, it averaged 44 :s, which isn't bad but i expected more!
I'm getting about 500 miles max on a tank. It also feels a bit powerless, but it is only 143hp!
I'm gonna drop it in tomorrow and let them have a look!
I think you are answering your own questions here.
80mph and expect good economy out of an 318d auto? The 318d manual saloon does 53.9mpg (on test) at 70-mph motorway cruising. The auto at 80-mph will fair much worse.
Feels powerless... if you you are working a small engine/auto hard, economy evaporates, always has and mpg is no better than a big engine with an auto box attached.
Remember at higher cruising speeds the bigger engined cars can get virtually the same mpg as the 'baby' engines. They can run lower boost due to plenty of torque at low throttle settings and benefit from higher gearing.
Don't get hung up on comparisons with others either, no two drivers have the same driving. One mans 'town' driving is another's 'heavy urban', at double the consumption.