John, after I responded to your PM, I found this post. I agree 100% with Rob Love. I think modern diesel multigrades are the way to go. We use Shell Rotella 15W40 because it is loaded with ZDDP which is an important anti-scuff additive that got taken out of modern automotive oils because it contaminated the cat. ZDDP protects the rubbing contact areas between flat tappet cams and lifters or overhead cams and rockers like the Meteor. When roller lifters became the norm in gas engines, ZDDP was quietly removed from the oil. It drove the engine rebuilders crazy because older engines with flat tappet cams would mysteriously wipe cam lobes after a few hundred miles. The oil manufacturers eventually admitted they had taken out the ZDDP. That's why there are so many ZDDP additives on the market now.
So an oil like Shell Rotella 15w40 suits the Meteor engine because the ZDDP protects the cam lobe to rocker contact surfaces, and the low viscosity of the oil when cold ensures oil gets pumped up quickly to the cams.
One concern i have with this oil is if you have been running a non-detergent oil for a long period, the strong detergents in Shell Rotella will start to dissolve the inevitable sludge built up throughout the engine, especially the oil pan. If the engine only has a bypass filter system, this is not good for the bearings.
Malcolm
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