Engine that has not run for over a year and now...

Boss 351

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Jul 13, 2003
2,433
23
48
Canada
Long story short: My 302 has not run in about a year when it was in the van, then when I put it in the Mustang it was in storage for a couple of months. It runs fine and everything but I wonder if I should change oil sooner (new oil in before I started the Mustang). This was 1000kms ago, I'm thinking about changing oil and filter to see if there was any crap in the oil filter. Before doing that I feel like using transmission oil a little to help clean the lifters or some kind of flushing agent?