I don't think that would explain why the oil light is coming on. You might want to check the oil sender unit (and connection). It would be wise to attach an oil pressure gauge, to verify the engine is not facing a major overhaul. Don't ignore an oil light coming on.

If you have a sludged up engine, look into Auto-Rx. It will safely clean a sludged up engine. To prevent sludging in the future, use a full-synthetic 5W-30 engine oil; e.g., Mobil 1.