when I was commuting a fair distance, 40-50 miles each way, some in heavy traffic, but when moving, 85-90mph, I used to average on LPG 16 to 17 real MPG, which based on the % price it was of petrol, I equated to roughly 30MPG, and I was quite happy with that though always felt it ought to have been getting more like 18-20 real mpg.

I did account for the 5-10 miles per tank I did on petrol and subtracted this from the odo per tank ful of LPG to get a fair result.

Now I am doing short commutes and very slow stop start traffic all the way (7.5 miles takes me 40 minutes!) I only get real MPG of around 12-13mpg using the same calculation method, which equates to only around 23mpg petrol equivalent.

I still feel though that I am saving good money relative to petrol-only, and my equiv lpg results compare favourably to the previous 3-litre bmws I have had, which returned similar petrol figures as the lpg equiv on my 260, so given the bigger V8 I think that's reasonable!