I assume you mean a race suit-as it is oil try fairy liquid neat but sparingly applied with a damp cloth, vanish might work too or even try some of that inorganic green (as in green product, not green colour) washing up liquid from Tescos. Whatever you use make sure it is not one of those solvent based cleaners. You could also try the company who made it for advice as it must be a common problem and they might even have cleaning stuff themselves. Hope this helps.
Buy a black suit Ctd!!!!
Ah no seriously, I've been washing my suit in the good Auld Washing machine for a good few years now and it doesn't do it a bit of harm......think there's a label on it anyway advising on what machine settings to use etc....I just hand it to me Ma!!!!