Oil and oil filters

I have been looking over the threads on best practice for oil and oil filters and there has been a lot of back and forth.

I have an 89 supra sunsport 351 Ford pleasurecraft motor. My spec book calls for 10w 30/40. But I see alot of knowledgeable people here saying lots of different things.

Some people say use a diesel engine oil for better protection for the work these motors do underload. Some saw bump up to a 15w-30/40.

I know oil is a pretty simple thing for the most part check it, change it, and done be cheap with it and you should be good.

But for an older motor like this should I bump up the weight to 15w...is the diesel oil a real improvement? I got some new Ford oem 10w-30 wondering now if I should return it for another type???

Also, marine vs auto oil filters don't seem to be much different. Any real benefits to getting.a marine one?

I would stick with oil for gasoline engines. Diesels see different contaminants since they burn different fuel. They run slower and see no vacuum like your engine does. In general, an engine runs best with thinner oil. As it wears, though, it will lose oil pressure under load, so a thicker oil will offer more protection. In the end, use a quality oil of any weight shown in your engine manual, and don't worry about weight unless you see very low pressure while idling..a sign of bearing wear. If you start to see low idle oil pressure, move up a grade. By the time you get to 20w-50 and are still seeing low or no idle oil pressure, then it's time for a rebuild.

The first number is the cold viscosity...so think of that as the starting weight. Since we rarely run our boats in cold weather, the more important number is the second, or hot viscosity weight.

I just use off the shelf filters. I have never had trouble getting the recommended filter from Oreilly's or Autozone. I couldn't tell you if it's a marine filter or not.

In my 89' Conbrio, I used Castrol 20W-50 conventional oil. I had the boat for 24 years and logged over 1500+ hours on the 351 Windsor motor. I took the valve covers off in 2015 to replace the gaskets and the heads look factory new. I only ran my boat in 75°+ weather. I would NOT use this in colder climates. My 2004 Supra(350 GM) called for Pennzoil 15W-40 in the manual, which is generally used in heavy duty service and diesel engines. I am using the Shell Rotella and have had no issues. I used a Mobil 1 filter as it is better constructed than most filters and, according to testing does filter better. When I slalom skied, the engine was running between 3000-3500 RPM, which I don't believe 10W oil offers enough protection. Automotive engines don't see the sustained higher RPM that most boats do.
Just my 2cents.

Mobil 1 15W50 is recommended by Mobil in all flat tappet and roller lifter engines . It is available at Walmart $ 22-26 for 5 qts . As for filters any will do except Fram orange . I use Motorcraft FL1A . Change at 50 hours

Yeah...it had the motorcraft filter in it so I just replaced that.

I found an oil by valvoline clef VR1 that said it was for flat tapped engines with added Zinc for protection. They call in a racing oil it was a few bucks more expensive but figured I would give it a shot. I think it was 20w-50 or 15w but I am interested to see how it goes.

Thanks for the feedback here guys