Oil Condition After Overheating

Maintenance/Repairs
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1

Had a couple bad freeze plugs that made my old 91 D150 with a 318 overheat severely. The truck is repaired but does smoke a little more than it used to at start-up and lasts a little longer. Also when stopped at traffic lights, It will belch a puff upon acceleration. Did the overheat affect oil condition and should I just go ahead and change it? Should I run some Marvel Mystery Oil through it before the change to maybe (hopefully) loosen up the piston rings? I know the valve guide seals are due for replacement but that’s another project down the road.

P.S. I’ve decided not to do anything with the fuel filter on the Camry…Was thinking proactive PM

2

Severe overheating can break engine oil down but it can also score/glaze cylinder walls or seize piston rings into the ring lands.
MMO is a shot I suppose for an oil coking problem but it will do nothing for a cylinder wall or heat seized ring problem.

Valve guide seals can certainly cause smoke upon startup or a puff on acceleration.