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Poppycock. I switched, from Dino Oil to Synthetic on an Engine with 110,000 miles on it, and it didn't leak, or burn it any faster. It now has over 250,000 miles on it and still No Difference.
Agreed I switched several cars over from dino to synthetic over the years no issue, including my boat. After repower the warranty required dino oil for first 100 hrs.
We are turnign this into another bottomless pit oil thread. The biggest issue OP should concern himself with is he has a flat tappet cam most modern oils dont have the same amount of zinc as oils used to. Use rotella T4 for this reason and dont over think it
Dino oil is fine. Synthetic oil is fine. Just make sure the oil has sufficient zinc and is of the proper viscosity and all will be fine. Synth oil will not cause your seals to leak, etc.
GM used to, maybe still does, market an Oil Supplement, aptly called Engine Oil Supplement(EOS) which they recommended during Break In. I recall the printing on the Can, saying it was good for Cam Break In. It was a delightful Chemical Stew, that while Thicker than Oil, it was runny compared to the Oil Honeys that did nothing.
The conventional Merc 25/40 has about 940 ppm of zinc, the syn blend 25/50 has 1240 from my oil analyses
Like I said a cheaper option is Valvoline VR-1 20/50 that has 1400 ppm of zinc.
On my engine it doesn't matter that much because it has a roller cam.
