Fuel (& the lead it contains) does mix with crankcase oil in reciprocating internal combustion engines, though it is normally in very slight amounts.
Compression and oil control rings prevent most of this undesirable mixing, but not completely.
During overly fuel-rich conditions, traces of fuel mix with the film of oil clinging to cylinder surfaces. If an engine is "flooded", most oil is washed off cylinder walls and puddles around the pistons. (In extreme cases, it "ponds".) Before firing, some diluted oil is pushed past the rings on compression strokes where it mixes with the oil in the crankcase. Worn or damaged engines let more of this occur.
Draginmopars,
That garage is outrageous . . . a grand idea, sir.
What sort of plane had a fuselage that fat? A C-130?