keppler wrote:Somebody else who drives a 90 might be able to give you ball park figures of their fuel economy, just to compare?
Now there's a red rag to a bull

I can get my graph out again:
This is mostly on a daily 70 mile round trip on the M4 in Berkshire -- which is flat. The most interesting thing here is the seasonal variation. HDis hate being cold, so if you're doing short trips (it takes about 10 miles to get my 90 up to temperature in the winter) then you may be better off with a petrol. On my current 10 mile commute I'm getting about 55.
The 90 is slow, but is capable of remarkable economy -- both in town and on the motorway -- but not if it's hilly because of the very narrow power band. In a flat town you can dribble it round on no more than 1500 rpm. On the motorway it'll do 60 to 70 MPG at 55 to 60 MPH, and down to 50MPG at 70 to 75, above which it gets very thirsty.
If you need to get your clog down then go for the 110. If you can accept the slowness in return for extra MPGs then go for the 90.