* Fuel Pressure Regulator (FPR) Function: The FPR maintains consistent fuel pressure in the fuel rail. It does this by regulating excess fuel pressure back to the fuel tank. A faulty FPR can fail in a few ways:
* Diaphragm Failure: The most common failure is a rupture or leak in the FPR diaphragm. This allows fuel to leak past the regulator, and since the regulator is typically connected to the intake manifold vacuum, the vacuum would draw fuel *into* the intake manifold (where it would normally get drawn into the cylinders). However, if this leak is significant and the fuel pressure is high enough it can overcome vacuum and force fuel *past* the intake manifold into the engine. Fuel in the engine then contaminates the oil.
* Stuck Open: If the FPR is stuck open, it constantly dumps fuel, creating the symptom of fuel pressure at the injectors (because the fuel is simply dumping past the regulator). It will also cause excessive fuel consumption.
* Gas in the oil: This is a critical symptom. Fuel in the oil will dilute the lubricating properties of the oil, leading to engine damage if not addressed immediately. It can also cause a loss of engine compression if prolonged.
* Gas at Injectors but not Throttle Body: In a properly functioning system fuel pressure is usually before the throttle body. Because your FPR might be leaking fuel directly into the intake manifold or beyond it into the engine, some fuel may be bypass the throttle body entirely.
Other Possibilities (less likely given the symptoms):
* Fuel Injector Leak: While less likely, a severely leaking injector *could* contribute to fuel in the oil, but it wouldn't directly explain the lack of fuel at the throttle body in the way an FPR failure would.
* Cracked Intake Manifold: A crack in the intake manifold *could* allow fuel to enter the engine, but typically you'd also notice a rough idle or vacuum leak symptoms.
What to do:
1. STOP DRIVING THE CAR IMMEDIATELY: Driving with fuel in the oil will severely damage your engine.
2. Check the Oil: The oil will likely be noticeably thinner, darker, and may smell strongly of gasoline.
3. Inspect the Fuel Pressure Regulator: Visually inspect the FPR for any signs of damage or leaks. This requires some mechanical knowledge and access to the fuel rail. If you're not comfortable doing this, take it to a mechanic.
4. Professional Diagnosis: It's highly recommended you take your car to a mechanic for proper diagnosis and repair. They can perform a pressure test on the fuel system and determine the exact cause of the problem. Replacing the FPR is a relatively inexpensive repair, compared to the potential cost of engine damage.
Don't delay addressing this issue; continued driving with fuel in the oil will likely lead to costly engine repairs or even a complete engine failure.
