I have a friend who runs a white diesel estate...The guys pretty clued up with mechanics and such like and swears by running his car on pure vegetable oil, straight from the supermarket.
This is of course environmentally friendly, but for some reason seems to cause a hell of a mess all over his paint. I think it's something to do with a rich mixture and thick oil spewing out of the exhaust. Anyways, he'd done 8000 miles since the last time he washed it and the car was literally covered in oily black spots all over the paintwork, but worse at the rear.
He initially started washing with regular car wash, but when this had no effect he thought he'd step up to household washing up liquid. Nothing overtly unusual with that, as I know certain people swear by the dawn wash thing.
When he realised the fairy liquid was no good, he stepped up to neat kitchen cleaner, which in fairness started to shift it, but it was by no means gone.
In a last attempt to get rid of the oily mess he cracked open his wifes highly potent Fryer and oven cleaner, using it neat and allowing it to penetrate for 5 minutes before wiping...As per the instructions you understand!!:scared
Low and behold, this final bid to rid his stead of these unsightly marks had done the trick!!
What I found to be even more impressive was the fact that he still had a paint finish to apply his turtle wax straight on to...Great job!!!!:shocked