Oil stains on caravan

Hi returning from Wharfedale oblivious that the car had an oil leak the oil was drawn under the car and sprayed up onto the caravan.  On arrival home and discovering the mess we immediately pressure washed the caravan however stains still remain.  We have tried pressure washing, steam cleaning, washing up liquid, Auto Glymn intensive tar remover, clothes washing tablets, petrol and brake fluid.  The worst affected areas are the front grab handles gas locker box and the rubber seal which runs the full length of the caravan on both sides.  Could anyone offer any advice please. Lorraine