Noisy engine on a 2010 Corolla LE

#1
My 2010 Corolla’s engine has started getting noisy when accelerating after hitting 2000 rpms. It’s a zzzzzzzzing noise that remains there until the transmission shifts at about 300p rpms. After the upshift, there’s a mild clattering, almost diesel-like. The clattering isn’t loud, but the zing is getting to be noticeable. Mileage is light for a ‘10. 65k. My guess is that the valves need adjusting for the zing sound, or possible replacement. The clattering I have no idea. I’m hoping it’s not the cam shaft.

Any ideas? Thanks.
 
#2
Follow up—after some google/YouTube research, I tried starting the car with the oil cap off. Got steady puffs of air and a little spray of oil, so now I’m thinking worn or stuck rings. Ahs anyone tried freeing them with crankcase additives?
 
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