A pint of Seafoam in the oil will help loosen up the carbon stuck piston rings, and help them to seal to the cylinder walls again.
Have saved a lot of oil smoking engines by letting that seafoam soak in there for a couple weeks after warming up the engine.
Then change out oil and fresh filter. The old oil is going to be really black after dissolving that carbon.
As your first oil change was really black in the first place, so it could use a good seafoam clean up.
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