you will get a hundred different suggestions on what oil and weights to use. just make sure you use 1 bottle of ZDDPLUS oil additive with every oil change to make your oil have an SF rating to protect your cam n lifters. Im a Pennzoil guy using 10w-40 in my 389. NOT synthetic, but that's just me.
When I had my all-original 389 in my 66 rebuilt, it was done by the gentleman that built the winning engine for the 2002 Daytona 500. He worked for Bill Davis Racing until such time as the team was shut down. After that, he opened his own shop and started building (and rebuilding) engines for muscle cars, hot rods, street rods and classic cars.
He highly recommended the Brad Penn oil and used Brad Penn for the break-in oil.
I have no affiliation with Brad Penn, but there is a lot of good information on their website. They operate the former Kendall / Amalie Refinery in Bradford, PA.
As mentioned earlier, their oil has ZDDP, essential to engines like our 389.:smile2:
I am in the same situation with how to work with this GTO I recently bought. The manual indicates that the tri-power should use only 30 weight. This is not easy to find anymore. Can a multi-grade be used and what weight should it be?
I think that everyone has their own idea but let me add my 2 cents worth. If the manufacturer states 10w30, then use it. I've been using Castrol GTX High Mileage for years with no problems. I substitute a quart with Marvel Mystery Oil (its been around for a long long time), change the filter and add ZDDP. For about the last 10 years I've used a filter magnet-it attaches to the filter and traps microscopic metal from moving around the engine. It's called Filter Mag. Just go online and read about it. Good luck!
10w30 with a ZDDP additive is just fine. I too agree that the Brad Penn oil is excellent. Been running Rotella in mine for years, though. The main thing is to not use racing oil, and to stay away from 20/50. Racing oil is not formulated for street use (missing the additive package) and 20/50 is too thick for non-worn-out engines.
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