Dum-Dums Bianca GTi6

[Ed Doe]

My friends parents had an LPG van for their business and the nearest station to here is Southampton, so they'd have to do a ~65 mile round trip just to fill up

That on it's own would surely negate any actual fuel saving over regular petrol...

And Dum, just re-reading your post, you can't just bung a load more in to increase the calorific value of the charge; that;s like throwing more petrol in; it'll just run rich if you can't get enough air in to burn it... unless I'm misunderstanding how LPG conversions work, in which case I'm happy to be educated!