Small Engines (Lawn Mowers, etc.): 18HP briggs and stratton /MTD, briggs and stratton, diaphram

Question
Why is gas in my oil.

Answer
One of two reasons.  The fuel pump has a bad diaphram that is allowing fuel to enter the crankcase via the pulse hose/passage.  The other problem may be the needle and seat in the carb are not sealing properly and is allowing fuel to flood the engine.  Hope this helps.