On my 94 Chevy blazer, gas in the oil was caused by a ruptured diaphragm in the fuel pressure regulator that is attached to the fuel injector.
Flooding the engine. An over abundance of gas in your cylenders will wash down your cylender walls and accumulate in the oil pan.
blown head gasket
one small posibility is one cylinder is not firing and fuel condensing and draining into oil. if the engine runs rough this my be a possiblity. but #1 is most likely.
Another possibility, but only for older cars with a mechanical fuel pump is a leaky fuel pump. It is entirely possible for these pumps to leak fuel directly into the oil.