Interesting reading, Eeek!!!! - thanks for the link. But that "petrol is death to diesel engines" bit strikes me as a bit OTT. I'll be submitting my diesel car for the NCT soon, and all the garages/mechanics I've spoken to recommend throwing a fiver's worth of petrol into the mix, the week before the test. Apparently it burns off all the deposits and temporarily makes your emissions that bit "cleaner"... not that I really believe I'll be failed on that particular item!