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Engine oil on the dipstick smells strongly of unburned gasoline: Causes & How to Fix It

If your vehicle is showing engine oil on the dipstick smells strongly of unburned gasoline, here are the most likely causes and the parts you'll need to fix each one.

Most likely causes

Leaking or Stuck Fuel Injectorurgent

A fuel injector is failing to close completely, allowing pressurized fuel to drip into the cylinder after the engine is turned off. This raw fuel washes past the piston rings and directly dilutes the engine oil in the oil pan.

High-Pressure Fuel Pump (HPFP) Seal Failureurgent

On modern direct-injection engines, the HPFP is mechanically driven by the camshaft. If the pump's internal shaft seal fails, it pumps high-pressure gasoline directly into the engine's crankcase, heavily contaminating the oil.

Frequent Short Tripsmaintenance

Driving only short distances prevents the engine oil from reaching full operating temperature. Normal fuel blow-by never gets hot enough to evaporate out of the oil through the PCV system, leading to gradual fuel accumulation.

Ignition System Misfireurgent

A failing spark plug or ignition coil prevents the air-fuel mixture from burning in one or more cylinders. The unburned gasoline then washes down the cylinder walls and mixes with the engine oil.

Engine Running Too Richaddress soon

A stuck-open thermostat or faulty coolant temperature sensor tricks the engine computer into thinking the engine is always cold. The computer continuously injects a rich, heavy fuel mixture that eventually washes past the rings and contaminates the oil.

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