What do you think?

 

Oil & Lubrication - Ford Truck Enthusiasts Forums

https://www.bobistheoilguy.com/forum...s.php?ubb=cfrm

There are the two best battle fields for the oil wars...

 

I use Delo 400 15W-40 in my 300. Cold idle oil pressure 60 PSI, hot idle 25 PSI. Was using Penrite 20W-60 but think this was too much for a recently reco 300.

 

I use Rotella in mine, and just about everything I own except the HD. Rotella is comparable to Delo I think. Oil opinions are hotly debated for sure.

 

Shell Rotella would be easier for me to buy here in Aus, but I can get Delo through Caltex service stations.

 

You can use HD engine oils if you do not have a catalytic converter.
Comparing Gasoline and Diesel Engine Oils

 

Thanks for link. We did not change over to unleaded gasoline until 1986 here. No problems with a 1978 F-100!
When the 300 was reconditioned the engine rebuilder recommended Penrite 40W-70! I baulked at that recommendation and went to Penrite 20W-60 instead. The Delo 15W-40 is a good compromise.