What oil do you use in your engine?

[IDBoating]

From Mobil's website...

>>From an engine performance viewpoint, the API CJ-4 oil should provide adequate protection. But this heavy-duty viscosity grade has a higher level of phosphorus than typical ILSAC GF-4/API SM oils designed for today’s light-duty trucks and cars. This higher phosphorus level can potentially shorten the life of expensive emission control equipment including the catalytic converter. We recommend you stick with the oil recommended in your owner’s manual.<<

...from:

https://www.mobiloil.com/USA-English...s_Engines.aspx

So it may work great in normal exhaust engines, but my in CAT equipped engine it doesn't sound like the best choice.

[IDBoating]

Tried NAPA this morning - no luck.

To their credit, they called Pennzoil while I stood there to ask them the question. Their statement was that 15W-40 diesel-rated (CJ) oil is perfectly acceptable. I have sent an email via PCM's website "Contact Us" mechanism asking if they agree with that... we'll see if they respond. (I have two pending website questions with them. They have never responded yet, but I continue to be hopeful. Funny that they have the "Contact Us" mechanism but seem to ignore it.)

[Joeprunc]

I've got the old 350 Mag MPI I use Chevron HD 30wt. I had a really good sludge problem from using Penzoil in another car (it was always the cheapest oil), but I'm sure their Marine grade is 100 Xs better.

[whitlock87]

I have a Marine Power, and it uses HD 30.

[chpthril]

You should find the recommended 15W-40 at your local marine supply. Merc and Pennzoil offer it, West Marine has it under their own label,

[IDBoating]

I have the PCM EX-343 engine. The owner's manual says to use 15W-40 oil rated for GF-4/SM service. I use 15W-40 in my Cummins diesel engines, and after visiting my local auto supply house today it appears that ALL 15W-40 oil is rated for diesel use - NOT gasoline. The ratings are different than GF-4/SM (for example, the S indicates gasoline service).

The PCM manual says in 50F and below you can drop to 5W-30. But that's not the prevailing temperature when I'm using the boat.

I'm thinking perhaps going to 10W-40 (possibly the most common oil out there) but the manual doesn't actually say to use it.

What does everyone here use? Thanks!