Gasoline in the oil is indication of fuel leaking past the needle and seat when the engine is not running (also high pressure in the fuel tank). You may be able to continue to use the generator with weak needle and seat (change oil) , however you must shut off the fuel when the engine is off. Easy fix however by installing carb kit. Find model number of the engine (stamped on fan cover) and contact small engine repair shop or look on line. Do not run the engine with gas in oil. Good luck.