Planes from the start were only ever given an "oil" damage hook, at least from what little I've seen so far. If hooks existed for, say, "coolant" and "radiator", we could have greater variety. A coolant leak should then terminate when the fluid runs out.
In code, oil is treated completely separately from the engine. As the engine goes through its various damage states, reflected by the evolution of its 3 smokes and fire, the oil damage effect remains always active once initiated. Including when the plane is on the ground--landed or cracked up.
I've tried to introduce into AircraftState.class an additional effect, that being for oil once on the ground. The engine and tank effects have ground equivalents, but not oil. I make the ground smokes subject to the wind, but becuse the oil smoke is for application at speed, where I make wind effect zero like the other engine/tank smokes/fire, on the ground the oil smoke clings to the plane while the other smokes drift away.
Makes me wonder if overall it might be better to make the oil damage smoke a bit subtler, and/or of shorter duration.