Engine Flooding

• If something prevents your engine from starting quickly, the prolonged starting period may cause excess gas to accumulate within the engine. When you turn the ignition to start your engine, you feed fuel to the engine. Fuel continues to enter the engine as long as the ignition is engaged and, if it isn't burned away, an abundance of gas builds up. This extra gas will wash down your cylinder wall and accumulate in the oil pan. One factor that can inhibit your Mule's ability to start is the choke. The choke pull is located next to the steering wheel, and should be pulled out to start the engine.
  
  

Bad Spark Plugs and Misfiring Cylinders

• When a spark plug is fouled, it causes a cylinder to misfire. If the cylinder fails to fire, fuel can condense and drain into the oil. However, a fouled spark plug can be both a cause and a symptom of gas mixing with oil, so replacing the spark plug alone may not be sufficient to prevent the two fluids from mixing.
  
  Check the plugs on small vehicles like the Kawasaki Mule regularly. In colder climates, where the vehicle is likely to be stored during the winter, check and replace spark plugs when the weather warms and you prep the vehicle for use again. In warmer regions, where you may drive the Mule all year, make checking the plug part of your regular maintenance schedule. If you find a bad plug during these checks, test your motor oil for contamination as well. If you find fuel in your oil pan, you can begin to troubleshoot the source of the problem.
  
  

Carburetor Problems

• If your carburetor is out of adjustment, your engine performance is affected. Lowering your carburetor's output will cause the engine to sputter, fail to start or die due to lack of fuel. Increasing the output sends too much gas, which will then wash down the cylinder walls into the oil pan in the same manner as it does after flooding. A badly adjusted carburetor often also results in a fouled spark plug, so checking your spark plug is one way of determining whether or not the carburetor is transferring the proper fuel mixture for your engine. A spark plug affected by too much fuel will exhibit some blackening near its tip.
  
  

Engine Wear

• Piston rings and cylinder walls can become worn over time. This wear is especially notable in engines that do not receive regular oil changes. As the oil becomes filled with particles, its effectiveness as a lubricant diminishes and engine wear increases. Worn rings and cylinder walls allow oil to enter the combustion chamber of your engine. Once there, it mixes with gas. If your engine is unable to burn away the mixed gas and oil, it drains back into the oil pan and contaminates your oil.