Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
Gas leaking into the oil is always sign that the carburetor needle valve and float are not shutting off the fuel. Do you have shutoff between fuel tank and carburetor? Did you leave it open? This only happens between uses , when the generator is not running.
Very unusual, but if it is, the carburetor needle and seat, controlled by the float is fault.
I have never had any luck with fuel additives, but it may help. Best to keep fuel shutoff between uses.