Question about engine flushes
Hello, I recently bought a 1998 firebird with an ls1. The previous owner said she used valvoline VR1 conventional oil for the car. Searching in the glove box, I found a oil change receipt for synthetic oil in 2020 and a receipt for 1 qt of VR1 in 2023. I believe the previous owner only topped off the oil with VR1. My friend recommends doing an oil flush with seafoam to clean out the conventional oil.
My question is that I saw on many forums online warning on doing an engine flush. Is an engine flush necessary in this scenario?
And if I were to do an engine flush, would I need to replace the spark plugs as I have just spent a day replacing them lol.
Car has 250k miles and a claimed 80k miles on the engine and trans. Unknown service history other than the mentioned receipts in the glove box. The car runs and drives pretty well.