Talk about embarrassing. You divide by 1.200, not multiply, to go from 
mpIg to mpUSg; i.e. from Imperial to US. So David C's 24 mpIg works out to
a precise 20mpg (US).

Don't ask me what I do for a living. And please don't report this incident
to my Dean.

Neil Wigley
U of ... uh, I forget