This may be a surprise to you but a diesel engine is different than a gasoline engine. 20w50 is heavy
oil, you must have .0027 or greater main clearances to require 20w50. You must be running valve springs in excess of 400lb open pressure to need all the
zinc and phosphorous.
Bradd Penn 15W40 from jets with free shipping will pacify all your concerns. do not use diesel
oil in a gasoline engine, the additive package is incorrect. this is not 1975 anymore.