Gas in engine coolant?

Check oil/water several times a week.
Recently I noticed reservoir coolant was low with a funny discolored mixture on bottom. Took reservoir out and dumped contents. It had a very strong gas smell to it. Immediate thought was head gasket, but car doesn't smoke, has full power without a hesitation at all, nothing in oil (not milky) or transmission mission fluid and still maintains excellent gas MPG. Recently used Chevron fuel system cleaner in probably in a little over concentrated manner.
Any thoughts?