I have not seen the 15/50 at Walmart for a while. I keep checking. Last time I saw some was 2 jugs back in october.

I have been using Mobil 1 V-Twin in my 496 HOs
since the boat was new. Great stuff! I send samples
to Blackstone each oil change. I have about 270hours
on the engines and there is virtually no wear.

Thanks Hydrocruiser!

this explains the SN rating. Note the warning for flat tappet lifters.

http://www.aa1car.com/library/api_mo...ifications.htm

Explaination of the API ratings from the API web site:

http://www.api.org/certifications/en...010_120210.pdf

Explaination of the API ratings from Royal Purple

http://corvettes.about.com/od/basicm...ur-Oil-Can.htm

Pretty clear that high ZDDP is a must for flat tappet cams but a "nice to have" plus for other applications per the comments.

http://www.goldenmotorguard.com/cart/

Lots of zinc.

Ken

A number of articles mention ZDDP additives that one can add to the oil. What ZDDP additive products are available? Where can they be purchased. Pros and cons of stand alone ZDDP additives?

I would not recommend ZDDP additives. Oil manufacturers spend multi-millions of dollars on their formulations, and if you change the "recipe" by adding more zinc to a product that is formulated to not have it, you can cause foaming of the oil. Too much zinc will cause foaming therefore leading to reduced protection. Would you add an extra egg to your grandmothers famous cake recipe, because you thought it would be better?

Hi can any one please tell me wot Donaldson # filter would fit the merc 496ho thankyou

Since they removed some of the Zinc, I have used this in anything I am concerned about. My oil of choice in the boat is Mobil 1 V-twin, with a Wix racing filter. http://www.cam-shield.com/ Their site is informative. Not for use with anything with a catalytic converter. Doug

Based on what I found in other threads the 496HO will use an AC-PF1218 which crosses to the Amsoil Donaldson EAO24. Give me your Merc part number and I will verify that this is correct. If you can tell me how much room you have below the filter, I can see if they have an oversize that will fit in it's place.