which oil weight to use on 89 PCM 351 engine?

[89Mariah351]

I have no sticker on my engine or boat to tell me what weight is recommended.
Seems I've got some oil coming from under the valve covers onto both my exhaust manifolds .. smokes after warming up. I was thinking I've got the wrong oil in there maybe. It's got Mobile 1 synthetic 10w-30 in it now.

Thanks for your time!

[88 Supra Comp]

I am by no means an expert engine guy...........but the guy I bought my 88 Comp from swears by: Castrol GTX 10W 40. I have not idea if that is a good oil...........although so far it runs great.

He however also added the following all new as well: MSD Ignitioin, Petronix Coil, Edelbrock 600 CFM Carb, Holly Electric Fuel Pump, Bosch Starter, Plugs & Wires, Ignition Switch.

So, don't know how much is due to the oil, or the rest of the above. I have been curious myself if I am running the "right" oil.

[Brian Raymond]

10W 40 is the proper oil to use on the older Ford 351. Brian Raymond

[DKJBama92Mariah]

Brian,

The sticker on my '92 351 Pro Boss says to use 20W-50. Should i use the lower weight?

DKJ

[84SunsportOwn]

I have been told by a Supra dealer to use 20w-50

[1988comp]

At high altitude, my 1988 PCM 351W uses Mobil-1, there is no other oil to use in any vehicle.

When mobil-1 first hit the market, it was what is now known as Mobil-1 extended mileage, that goes to 15k miles between changes.

You can buy that oil again, and it is unbeatable. If you want even more protection, like if you have a supercharger or nitrous oxide, use the Mobil-1 motorcycle oil.