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I've heard that from a lot of different people but can't seem to get a consistent reason why. What's the reason you don't run synthetic oils during break-in? Ring seating?


becuase it's too dang good at preventing wear.
there are more than a few that say the rings and bearings won't run in right unitl they got some solid wear between everything. that bieng said, every new corvette is delivered from the factory with Mobil 1 synthetic in the crank case. personally, I ran the first 20 minutes on my new motor with non-synthetic.

IF the new motor is built for synthetics with extremely tight tolerances and IF the manufacturer says so, sure, gopher it. For all else, I'd put at least 1500-3000 miles on it following Darin's regime before putting synth in. Rings won't fully seat for a very, very long time. Which itself is pretty powerful testimony for the value of synth oil.

I run DuraBlend because I'm cheap and I still want to change the oil often to remove contaminant fluids.

-Bill
'87 4Runner w/ '96 5VZ-FE, 'Red Chili II'
'97 Taco XtraCab 3RZ-FE, 'BlackBean'
TLCA # 13257, Rising Sun 4x4 Club Land Use Coordinator
"He who stops being better stops being good." -Oliver Cromwell