When engine oil smells like gas, it usually is the result of excess fuel getting into the oil. On carbureted engines, this typically comes from a leak in the fuel pump diaphragm. It also can be caused by an automatic choke that does not open completely, by a brass carburetor float that has developed a leak and become heavy with gasoline, by a plastic carburetor float that has become porous and is now heavy with gasoline, by excessively rich carburetor jetting, or from an idle mixture adjustment that is too rich.
Fuel injected engines are less likely to get excess gas in their oil; but it can happen if the fuel pressure regulator is defective or is set for too high a pressure, or if the exhaust oxygen sensor has failed or been disconnected.
If an engine is used exclusively for short trips, and thus does not get warm enough to vaporize the small amounts of fuel which accumulate in the oil during normal operation; this will eventually lead to the oil smelling like gas. That is why it is recommended to change the oil much more often, if a vehicle is used mostly for short trips.
I hope this helps!!!