Why is fuel mixing with engine oil in the crankcase?

What causes fuel to leak into my engine oil?

If you notice gas mixed in with your engine oil, follow these instructions to address a potential leak.

  • The fuel shut-off valve isn’t closed properly
  • Fuel float in the carburetor being stuck in the open position due to gumming (caused by stale fuel), tipping the engine resulting in the float rubbing on the carburetor bowl, or debris
  • Fuel pump is bad (if equipped)

How do I fix fuel leaking into my engine oil?

  • If your engine has a fuel shut-off valve, ensure that this valve is closed when the engine is not in use.
  • If carburetor problems are causing fuel to mix with your oil in the crankcase, you should perform a thorough cleaning. Find out how to clean your small engine carburetor.
  • Check fuel pump if equipped

For any other specific questions or concerns related to fuel and oil, make sure to contact a Briggs & Stratton Dealer near you. You can also find carburetor cleanerlawn mower oil and more service materials in our online store.

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