Which oil is recommended for best performance for a 351m engine in a '79 f150?

 

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Because the newer SM rated oils have had the additive packs reduced dramtically by comparison to when your engine was designed and built, I would suggest a dual rated oil like Rotella, Delo400, Mystic, Motorcraft Diesel, or Delvac if you can find it in 10w-30 would be ideal but the 15w-40 would also work. If you can't find any of that, use a quality SM oil with a bottle of CD2 Street Legal Oil Boost. It has a bunch of antiwear and friction modifier additves that you older engine needs. You will find the CD2 at places like the Dollar stores in a pink bottle. The other Cd2 products won't work. When the newer diesel rated oils come out for the newer mandated low sulphur fuel, even the diesel rated oils will need a booster of some sort for the older engines as the additive packages are going to be reduced a bunch.

 

be aware that oil additive often cause oil to froth...

i say the test of what ~5 of the most common additives and a test rig brought it to near 'real world' as they figured it oils ok like lucas at slow speed/rpm it climbed BUT as speed increased to it frothed very baddly

and boy that S...50 nice runs right off then frothed

basically the oil you buy is engineered with in a inch of its physical properties

i did put light synthetic oil in a worn 351m well at 5+ a quart i was rather unhappy it blew out the rear main seal
second time i started it i out smarted it i ran 15-40 in a 43 year old ORIGINAL 170 near a drop fell

you see its not the synthetic that makes it leak..
as reg oil is used sludge builds up in front of the seals starving them of oil drying them but the sludge also seals kinda
when you add syn oil the detegent is so high that it will strip the sludge faster than it soaks into the seals and WHOOOOSH

well in closing i am going to run a few hundred miles or thou and do a strong kero flush and then start with 20-50 to clean the rest of the sludge out then 10-30/40 once i get my motor installed