In reply to Basstard, many good points about the viscosity (someone earlier was right about PD Pumps-BUT Mercedes say all their Diesels will run on straight biofuel (cooking oil) But in my experience (through a friend of course) the only difference on that Rover TDI was in winter (we havn,t had a bad winter for ages-so things might be different in a bad one (or the Glens of Scotland) it took two turns of the engine to fire up instead of the usual one and has never had problems with dirty fuel lines etc. but it ru ns every day. (If I were worried about that sort of thing - hypothetically I would cut the cooking oil with parrafin (greenhouse heater type - which the EU decided has to be clear like vodka -so no colour to worry about and no smoke (incidentally TDIs seem to run OK on the parrafin also, purely foran emergency, such as a fuel strike or somesuch) (This is just a by the by, but years ago when I ran a diesel Merc an Italina guytold me that Diesel was so cheap in Italy because if it wasn,t everybody would run on cooking oil, in fact even then, 70s a lot of his relatives in the coutryside ran all their diesels on cooking oil as it was even cheaper than diesel.