It needs an oil change... are you sure it still HAS oil in it?
Stupid question, but my one friend said it was "time for an oil change", and he found out he had maybe a cup of oil in his engine.. that idiot.
If you're low on oil, and if the engine has higher mileage (causing more oil pressure to be lost at the crank and so forth), the valvetrain would be the first thing to be not lubricated properly.. possibly producting the harsh noises in there.
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