Recommend oil weight, type, brand.

[covertcombatant]

I have a 1988 Supra TS6M and was curious what oil everyone is running in their 351w. I have searched and mostly old topics come up, and I figured with oil formulas changing frequently to newer car demands that i would ask what most of you owners have been running? Sorry if it's a topic that has been hashed out over and over its just my first inboard and I want to learn everything I can on it.
Thanks for the input and help.

[UKandH]

I am using Royal Purple 20W 50.

[Cusefan78]

Rotella t 15w40 has the highest zddp rating which is the most important thing to look for in oil for our boats.

[DKJBama92Mariah]

On the recommendation of my tribologist (lubricant analysis expert) I have been running Shell Rotella T6 5W-40 Full Synthetic for the past 6 seasons with good results. Both Rotella T6 and the Rotella T 15W-40 conventional oil mentioned above have the Zinc necessary to protect the flat-tappet cam/lifters that our boats have. Both these oils are are heavy-duty diesel engine rated oils. Most modern automotive oils do not have the necessary zinc additives we need to protect our engines.

[covertcombatant]

Thanks, for the info. I ended up going with the Rotella in 15w40.
Thanks for the help everyone.