* Failed Fuel Pressure Regulator: This is the most common culprit. The fuel pressure regulator controls the fuel pressure in the fuel rail. If it fails, it can allow fuel to leak into the engine's vacuum system, eventually finding its way into the crankcase via the PCV system.
* Cracked or Damaged Fuel Injector: A cracked or faulty fuel injector can leak fuel directly into the cylinder or even into the intake manifold. This fuel then washes down past the piston rings and into the crankcase.
* Faulty Intake Manifold Gasket: A leak in the intake manifold gasket can allow fuel to enter the crankcase.
* Problem with the PCV System: While less likely to be the *primary* cause of significant gas in the oil, a malfunctioning Positive Crankcase Ventilation (PCV) system can contribute. If the PCV valve is stuck closed, pressure builds up in the crankcase, and if there's already fuel present (due to one of the causes listed above), it could exacerbate the problem.
* Damaged Piston Rings: Severe wear on the piston rings can allow fuel to pass from the combustion chamber into the crankcase. This is less likely to be the *sole* cause of gas in the oil, but could be a contributing factor, especially if the engine is high mileage or has been poorly maintained.
What NOT to do:
* Don't start the engine. Running the engine with gas in the oil will cause significant damage. The gas will dilute the oil, reducing its lubricating properties and leading to engine seizure.
What to do:
1. Stop driving the vehicle immediately.
2. Have the vehicle towed to a mechanic. Do not attempt to drive it.
3. Do not attempt to repair this yourself unless you have significant experience with automotive repair. This issue requires professional diagnosis and repair.
The mechanic will need to perform a thorough inspection to determine the exact cause of the fuel in the oil. They'll likely check the fuel pressure regulator, fuel injectors, intake manifold gasket, and PCV system. Further diagnostics may be required depending on their findings. Ignoring this problem will almost certainly lead to costly engine damage.
