View Full Version : Oil grades for marine engines vs. auto engines?

04-25-2013, 02:34 PM
I just spent $140 for 3 oil filters and 4 gallons of Honda Marine oil for my 2 outboards and 12.5Kw Westerbeke. The outboard’s manual says to use oil with API Service Category of “SG” or “SH”. At Wal-Mart, the only API Service Category I could find was “SN”. I’m not sure the difference between the API ratings, so I bit the bullet and just bought the Honda Marine Oil for $25 a gallon. I was surprised to find out this stuff isn’t even synthetic! Crazy thing is, I could do a Mobile 1 full synthetic change for the same price, but it would be the “SN” API and not the “SG” or “SH”.

What’s the difference between these API Categories and would it really matter if I used the Honda stuff or the Mobile 1 synthetic?

Most of you have marinized auto motors in your boats. Do your motors also call out a special API rated oil?

04-25-2013, 02:55 PM
Ok, it's a slow day at work, so I did some quick digging and found this document (http://www.api.org/oil-and-natural-gas-overview/fuels-and-refining/engine-oil/~/media/Files/Oil-and-Natural-Gas/Engine%20Oil/MOTOR_OIL_GUIDE_2010_120210.ashx)on the API's website. As it turns out, SG and SH are obsolete and it doesn't explain what to use in place of these grades.....

04-25-2013, 03:00 PM
I found the same website.... SN oil is for "..2011 AND OLDER..." so it should cover you.

04-26-2013, 07:31 AM
So, next question, do you guys use the dino juice or the synthetic in your boat motors? I personally love Mobile 1 synthetic in my 2 cars. Since it's synthetic, I have extended change intervals at around 7K miles, instead of the suggested 7.5K miles for synthetic.

Because I'm in the automotive industry, I know that synthetics are not suggested for older engines because the molecules are much smaller than conventional oils and seep past the gaskets. What's more, synthetics have more detergents in them, which breaks down older gaskets and seals that are not designed to withstand those detergents - causes leaks and smoking.

I'd like to be able to use synthetic in my motors and change the oil every other year. Using the dino juice, I'm compelled to change annually. What's your thoughts?

04-26-2013, 08:17 AM
i use valvoline 10w30 in my motors and generator plus lucas oil treatment. i change the oil every fall before i pull out.i also change all filters every fall.doing it myself it is pretty cheap peace of mind.

04-26-2013, 08:43 AM
The API designations are successive - SN trumps anything below it - SM, SL, .... As far as the rest of it, do what makes you feel good. It is doubtful that any engine would die of using the cheapest Walmart brand oil over using Mobil 1. Or, that a lightly used boat engine would suffer at all having the oil changed every other or even every third year. And, yeah I know all about the acids that build up and can ruin your bearings. Try to find someone that has actually seen an engine fail from that.

I personally use Penzoil - just a personal preference because that is what my dad used.

04-26-2013, 10:49 AM
The last time I actually saw acid eroded bearings was in 1956 in a 1949 Oldsmobile engine.

04-26-2013, 12:37 PM
Ok, but are you guys using conventional motor oil (aka dino juice) or are you using the synthetic?

04-26-2013, 03:58 PM
I'm now on the fence now as far as oil is concerned. In looking around on the web as far as the newest rating in oils I ran into some controversy. The newest release or rating may actually be detrimental in a way a poorer quality product than was previously available. In many ways opponents of the SN oil may have a valid point. One example posted below....

Think About Your Zinc

Have you heard about the zinc problem with modern motor oils? Many classic car owners and racers have experienced camshaft failures due to decreased zinc levels in modern motor oils.

Now, with levels about to change again this fall, it’s more important than ever for engine builders to think about their zinc.

If you’ve not had the pleasure of having your camshaft go flat due to modern motor oils, consider yourself very fortunate. As an owner of an engine parts warehouse, I’ve seen hundreds of perfectly good camshafts ruined by modern motor oils.

So, when I read about the new API SN motor oil coming out this fall, I started talking to the engine builders we supply parts to. They all said the same thing: car owners don’t know much about these modern motor oils and the problems they can cause in classic cars and racecars.

In many cases, modern motor oils are simply not good for classic hot rods and race cars. Here’s why:

“Zinc,” or ZDDP as it is commonly referred to, in motor oils is a type of chemical called Zinc DialkylDithioPhosphate. “Zinc” has been the most common anti-wear additive used in motor oils for the last 60 years. (I’ll just call it ‘zinc’ for the rest of this article.)

Zinc is a remarkable chemical that protects engine parts from metal-to-metal contact under heavy loads. It works by creating a film on the iron and steel parts in an engine.

Unfortunately, zinc also creates a film inside modern three-way catalytic converters. This “Zinc Poisoning” limits three-way catalytic converter life to around 70,000 miles.

The Federal Environmental Protection Agency mandates that car manufacturers warranty three-way catalytic converters on new cars built since 2004 for 120,000 miles. To achieve this goal, the car manufacturers worked with the American Petroleum Institute to create new, lower-zinc oils that allow three-way catalytic converters to live longer.

These new “Lower Emissions” oils have extended catalytic converter life, but they have shortened the life of flat-tappet camshafts.

Not long after these modern motor oils with less zinc hit the market, we started to notice an increase in flat-tappet camshaft failures. At first, it was the race engine builders, so we shrugged it off as some new “trick” the race guys were doing that caused the problem. Then we started to see stock flat tappet camshafts going flat.

Things got ugly really fast. Every camshaft company started researching the problem. So did the Automotive Engine Rebuilders Association. Everybody wanted to know: why are cams going flat?

The answer was less zinc.

Turns out, lower zinc oils work just fine in modern production car engines with overhead cams and roller lifters. These modern engines don’t rev past 5,000 rpm.

On the other hand, most hot rod and race motors have push rods and flat tappet lifters, and rev beyond 5,000 rpm. These engines need motor oil with more zinc.

The good news is that “High Zinc” oils are available.

If you have a classic car or racecar, I highly recommend using a higher-zinc oil. We use the Joe Gibbs brand, and there are others also available.

We have seen a dramatic reduction in camshaft problems when our engine builders started using higher-zinc oils designed for older engines.

Again, if you’ve not had any problems so far, consider yourself very lucky. But with the new formulas scheduled to be released this fall, switching to a high-zinc oil before the new API SN oils hit the shelves is like an insurance policy you’ll be happy you have.

We like selling engine parts, but I hate seeing good parts go bad—especially when they don’t have to.

Source (http://performancebiz.com/tips/think-about-your-zinc)

04-27-2013, 08:10 AM
I use synthetic in my cars - except in my 1968 Camaro. I use dino diesel oil in it for the zinc. My houseboat came with 10 gallons of Mercruiser oil - dino 25-40w - I will use all of it first, then decide what to use.

04-27-2013, 09:14 AM
They took zinc out of most motor oil years ago.

04-27-2013, 05:33 PM
They reduced it a lot. You can buy the additive or there are specialty oils that have the "original" levels of zinc in them.

04-27-2013, 07:16 PM
A lot of people like Valvolene VR1 for their flat tappet engines.

05-12-2013, 02:39 AM
i dont use any synthetic in the boat.

05-13-2013, 07:01 AM
Well, the weather cooperated for the 1st time in over a month, so I finally changed the oil over the weekend. I used the electic oil pump gismo that my brothers bought me for X-mas this last year, which made this job a sinch. I don't know how I over extimated the total amount of oil I needed, but I bought 1 too many gallon containers of Honda Marine oil to the tune of $26. I checked the dip sticks after I ran the motors for a few minutes and each is right on the money. I'm going to call back the shop and see if I can return the container b/c I don't plan on changing the oil until Spring of '15 - I don't use the motors enought to justify annual changes, but I'll play it by ear.