I have a '79 pickup with the 300... The engine is brand new. Not rebuilt. BRAND NEW. Anyways, I have run about 2 or 3 oil changes with conventional oil to get the seals set and everything and now I'm going to use synthetic. I'm not sure whether ill use Amsoil, Mobil 1 or Royal Purple. And I looked in the book for the recommended weight and viscosity but it doesn't really have a "recommended". What do or what would you guys use? Thanks

 

10W-30 mobil 1 is what I'd use in it. I think the other a just as good(no better) with a higher price tag.

 

The oil war battlefield is here: Oil & Lubrication - Ford Truck Enthusiasts Forums

 

I have a 300 six in a 1970. Motor was a cheapo rebuild 30K miles ago. Oil pressure was low normal and fluctuated a lot but ok. Recently lost oil pressure completely at speed. Killed engine promptly but you never know. Tore it down and bearings were worn but Miked it all and ok. I have no doubt the Mobil 1 high mileage saved the crank and PW cam.

Why was I able to shut it down so quick? Installed a Summit digital oil gauge and kept the idiot light. Light flashed, caught my eye, saw zero pressure and killed it. Digital is almost instant response.

Why high mileage? It has more zinc, maybe 1000 ppm.

Why no oil pressure? A jackleg in Ga on a rainy night repaired a stripped timing gear (that another jackleg had abused with a bearing press) and his jackleg nephew helper scraped cork gasket into the oil pan. Where it lay for two years and crumbled and gradually and then completely plugged the oil suction screen. Liquid tight.

What now? New bearings and 55 psi at all revs, maybe due to relief valve on oil pump. And nobody's touching my truck but me.

 

Shell Rotella T or Break in oils are all I use in a non roller engine. As for weights, winter it usually sees 5W30 or 5W40, in the summer its 10W30 or 15W40.

 

I bought a remanufactured 4.9 from ford for an 89 E150 about 5 months ago they installed the engine and they put Castrol 5W-30 Syntec in it. Oil pressuse runs about 48.