Fuel in oil

[dieselwill77]

I'm Getting fuel in the engine oil (Engine oil was almost a gallon overfilled after 3000 miles on the oil, and oil is thin I sent a sample out for analysis just to be sure).

I am thinking injector o-rings? Any one have any other ideas? The fuel in the filter housing is clean, and there is no fuel in the coolant

The truck is a 2000 and has 242,000 miles on it.