from firts thought it sounds to be a head gasket, but the petrol in the oil is really confusing, is there any other way petrol id able to get into the oil?

also it could be seeping somewhere into the head then leaking into the sump. anything is possible.

main problem is, if i cant see the car its hard to tell. can you possibly put some pics of it on here?
mabye i could help from there on.

sorry for not beign able to give much help at the moment.

but dont rule out the piston rings either, if they are completely shagged the injectors could be spraying small amounts of fuel down into the sump on each stroke, easy way to check if it is piston rings is that the car would be lower on compression for the missfunctioning cylinders and you will be able to hear a slight air leak if you take the dipstick out or mabye feel it.

is the car down on power or fine?