fuel shouldnt be a problem. change the oil. make sure u put the right amount in. also check the oil for bubbles(white foam, not ones caused by the oil fallin into the pan) or anitfreeze. that might mean she has a head gasket problem. is fuel getting to the engine? might want to check the fuel filters, possibly change them as well. yeah oil in the cylinders is bad. never a good thing(im lookin into the problem myself). when u take plugs out, does smoke lift from the cylinder chambers?