You can clean it with pretty much anything that cleans and isnt likely to cause corrosion but make sure its pretty dry before fitting (dont worry too much, anything exhaust side will be promptly burned off and anything inlet side will get burned in the engine) and prime the oil system before you start it up if you go cleaning the centre section out (or pouring tons of cleaner in there). Whatever you do, dont try taking the wheels off for cleaning, they are balanced and you will put this out by seperating the assembly which you "might" get away with but "probably" wont.
Its not going to make much of a difference to the cars performance though
.
