I had the opportunity to get a trade in quote on my current tractor for a John Deere 5000 series tractor. Part of the incentive was I recieved 2.5 gals. of John Deere Plus-50II CJ-4 SM diesel engine oil.
Naturally, I'd like to use this oil in my current equipment but my tractor uses 10-30 oil. The Mercruiser 6.2 and my '66 Dodge Charger can use the 15W-40 oil weight. I did look on the JD website and in the accompanying link they do recommend the oil for marine application.
http://www.deere.com/wps/dcom/en_US/...lus-50_ii.page

This oil seems to be a good match for the Mercruiser 6.2 but I know that there are some oil experts on this site that could probably shed some light on that. Thanks for all that reply!

not all diesel oils are approved for gas engine..too much detergent...make sure the one you buy is approved...read the fine prints

The specification you list for your diesel says it is a SM which means it a gasoline rated engine oil.

If the viscosity is what you would like to use, run it.

Personally, I think 10w30 is too thin for a boat motor.

Ken

Thanks for that information, Ken. The bottle that I have is 15W-40 weight so it would be the same weight as Mercruiser oil.
I like the TBN of 10.5, I think it was, because that's supposed to be an important number for antiwear characteristics. I didn't realize that the SM in the description indicated that it would be suitable for gas engine use.

I've been using the JD Plus50 for 5yrs now great oil, then the Plus50II came out still great oil been using for 2 or so years. the only oil I use...

Hematite, no problem.

The TBN number has nothing to do with anti-wear.

Zinc and phosphous are the modern anti-wear additives.

The "TBN" number has to do with acid neutralization the higher the number, the longer you can leave the oil in the motor. This is the short answer.

TBN's are not as important now as they were because all diesel fuel is low sulpher.

I think Mercury oil is a 25W40.

15w40 would also work fine.

Ken

Thanks for that feedback!

minxguy, thanks again for your follow up. Yes, you're right, the Mercruiser oil is 25-40. So the 15W-40 JD oil is not an exact substitute. The engine only has 31 hours so the 15W thinner viscosity may not be a problem. I don't beat on the boat so it may be OK to use.

They are both 40 weight oils when hot. 15w means it flow better than the 25w at a set cold temperature, but when hot, they should be very similar.

Dominator, that's true but the oil manufacturer has to use more plasticizers to go from 15W to 40 which I understand is a negative.
I also remember reading somewhere that Mercury doesn't use plasticizers but says that their oil is a blend of 25 weight and 40 weight. That never made sense to me since that means that the final viscosity is something like 32.5 single weight doen't it?