My car has sat for almost 3 months now with dirty oil in it, it wasent desperately needing an oil change but it was dirty enough for me. The car also has not been started since then either (cause of my supposed injector/wrong distributor issue). Its Castrol Syntec 5w-40, so its a good oil. Will it harm the engine at all being in there like that? What about on start up? Things i can do? Im just paranoid about these things and its probably nothing but i dont want anything bad to happen. My oil pan will probably be sludge lol.