Carver Owners Forum

Elsewhere on the forum is a topic on oil, where, as I read it, some are advocating Rotella, an oil formulated for diesel engines, for their gassies. Why? What are the advantages of this over 'normal' oils?

Ed

Great grade for our engines, The additives and detergents in it is amazing. Oil stays fresh and CLEAN through the whole season. Also, use the same oil in my motorcycle.

"What will keep a diesel engine clean fails to do the job in a gasoline engine because the deposits are different, the fuel is different, the running conditions are different, and the oil's additive package is different."
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Many disagree with this, based on experience. It is difficult to get a definitive answer.

edw wrote:Source of the post Elsewhere on the forum is a topic on oil, where, as I read it, some are advocating Rotella, an oil formulated for diesel engines, for their gassies. Why? What are the advantages of this over 'normal' oils?

Ed

There is a forum called BITOG ( bob is the oil guy ), there is endless amounts of lubrication info from oils to greases etc.....mucho reading..

Anyway for me this oil thing comes down to the type of engine you have, basically if it is a flat tappet cam build. Years ago, many years ago the oil I used for the boat and racing was Sae 40 kendall gt1...the green oil. It had the right additives to keep the cam from wiping. Due to environmental concerns the additive packages in oils began reducing the wear reducing zinc etc....this caused some problems. The quick fix at the time was racing oil ( read expensive ) or the diesel oils which were rated for gasoline engines at the time and had the package still there in the right numbers to protect the cams, especially if you had any kind of higher pressure springs.

So just a little history from my perspective, there is a lot more but I won't bore you with all that.....older engines like yours are my guess not roller cams so some protection will be still needed although not much as the cam will have been marinated over the years so to speak..

Diesel oils like rotella and mobil are fairly cheap and offer good protection....I mean once a year oil change for twins will be in the area of 12 to 14 US quarts total, maybe more if you run up the hours. So you can decide what your comfort zone is, but I still recommend bitog if you are interested in all the ins and outs of all the current day oils etc.

The newer roller cam engines don't need this level of protection IMO....just use what the engine maker recommends and all will be fine.

I used to be a big proponent of using Rotella as an alternate choice in gassers until I talked to someone who knows way more about oil formulations, additives, etc., and their affect on engines, it's his job. The science is actually pretty interesting but way more complicated than I can explain. What stood out more than anything was the amount of zinc (ZDDP) in the formulation as this seems to be a popular topic. Now most will tell you that zinc is a good thing, and I agree that it is, it has it's place in lubrication for sure, but too much in the hotter running combustion chamber of a marine gasser is detrimental over time, especially in a catalyst application.

It's agreed that higher zinc content is desirable for break-in periods, racing applications, and older builds with flat tappet lifters, but the amount of zinc in the blend is critical for each application. There is a fine line, too much is not good. Not all zinc blends are the same either. The zinc blend used for diesel oils differs from that of automotive and marine because of combustion chamber pressures. The difference is the zinc blend burn rate which is not the same for diesel vs others and is a concern when using a diesel blend in a gasoline application.

Other additives in an oil blend also make a huge difference in an oil's performance. These also need to be taken into consideration when using diesel blends in a gasser as the two have different requirements. The blend and level of detergents for example differs, but detergents wash zinc away so there must be a happy balance. The diesel blend balance works fine in a diesel engine but is not in balance when used in a gasoline application, especially a marine one.

There was so much more but this is what really stood out to me. I also read a very interesting and informative paper on-line, just wish I kept it, can't seem to locate it now. Look, in the end, each is going to use what has worked for them over the years but that's not always the best thing to do as there may be things going on that we're not aware of hence the old saying "it's what you don't know that will come back to haunt you." Still, you have to be comfortable with your decision. There's too many factors/variables at play, so you may get through decades and engines with no ill effects of using diesel oil in a gasser, or you may not. For me, what I've learned was enough to reevaluate my thinking.

I have 2 gallons of Rotella T4 15-40 left over from my diesel days, was hoping to use it in my 220s. But based on this thread I searched and found the manual online for the old Crusaders, and it turns out it recommends 10W30. So I will use that - from the marine store - but it may cost me close to or over $100 CAD for the fill. Maybe I can sell the Rotella . . .

Rotella makes a 10W30 too. And a 30W which I'll bet was on the filler cap, at least it was om our '86 5.7l crusaders. I not a fan of multi grade oils, guess I was brought up in the generation before multi grade oils.

Nothing wrong with multi-grade oils, just pretty much unnecessary in most marine applications. If you boat in very cold weather, it could make a huge difference, but in normal boating weather it just doesn't add much. However it's easier for the manufacturers and suppliers to sell a multi-grade because it has so many more applications than just a straight weight oil.