2 tanks will be ok. As for the oil don't worry this is because of the rich settings. Remember to do this after each tank and allow the engine to cool between tanks. remembering to set the piston at BDC. T o do this i took the gloplug out and pulled the started till piston was at lowest point, then marked the fly wheel with a black marker pen, this way you know where BDC is each time without taking glo-plug out.