Rotella T4 15w 40

[km1125]

Source of the post
The contamination is a result of the byproducts from the combustion process regardless of carbed or injected. Some of the byproducts are corrosive so you don't want some internal engine component surfaces sitting in that soup for very long, especially in a static state such as during winter layup. The damage doesn't happen in one winter but is accumulative and may become a problem over time.
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While I generally agree with your post, that first line is a bit misleading. Only some of that contamination is due to the combustion products and even some of those combustion products were much worse with carbs over open-loop injected engines, and open-loop injected engines are even worse than closed-loop injected engines. You can see evidence in this in the oil change intervals in cars when they made the migration from carbs to open-loop to closed loop. You could never run a carb engine with 10K or 20K mile change intervals, but it's not unusual in closed-loop systems and this is largely due to the contamination in the oil being greatly reduced.

It's not the filterable products or the 'dirtiness' in the oil that's generally the concern, it's the contamination that may not be visible that can cause significant long-term damage.

[bud37]

I think if I now owned Marine diesels or any diesel for that matter, I would seriously consider basing my maintenance on getting used oil analysis done and follow their recommendations as to the state of the oil and how to go forward. One good reason, is the high cost involved with diesels ( very large sumps ).

The same could be said for gas engines as well....it would give you a clear picture of the oil condition , then there would be real time analysis results to consult.

That said oil is relatively cheap but it is extremely costly and wasteful ( environmentally ) to deal with the waste oil if you don't have to.

[Viper]

Source of the post

Source of the post
The contamination is a result of the byproducts from the combustion process regardless of carbed or injected. Some of the byproducts are corrosive so you don't want some internal engine component surfaces sitting in that soup for very long, especially in a static state such as during winter layup. The damage doesn't happen in one winter but is accumulative and may become a problem over time.
....

While I generally agree with your post, that first line is a bit misleading. Only some of that contamination is due to the combustion products and even some of those combustion products were much worse with carbs over open-loop injected engines, and open-loop injected engines are even worse than closed-loop injected engines. You can see evidence in this in the oil change intervals in cars when they made the migration from carbs to open-loop to closed loop. You could never run a carb engine with 10K or 20K mile change intervals, but it's not unusual in closed-loop systems and this is largely due to the contamination in the oil being greatly reduced.

It's not the filterable products or the 'dirtiness' in the oil that's generally the concern, it's the contamination that may not be visible that can cause significant long-term damage.

We'll have to agree to disagree. While there are differing levels of contamination between the two types of fuel delivery systems, it still stands that many of the undesirable byproducts are the result of the combustion process itself. Even a closed loop system contaminates oil. Your final/closed measurement is after the exhaust sweeps through the catalyst, there's still plenty going on that's in contact with the oil before the catalyst. The byproducts in question may be minimized in newer designs but still exist/occur due to combustion none the less. You can't get away from that in a combustion engine, only strive to minimize it. Newer designs however mean tighter tolerances and less forgiving of undesirable conditions such as that of poor oil quality, contamination, etc.

Bottom line IMO is good regular maintenance by replacing your oil at least once a year in the Fall with a good quality marine oil that is formulated for our environment and running conditions. I can't understand why this seems to be a typical place to cut corners/costs on such a critical system/expensive piece of hardware, yet most have no problem spending thousands on less important things to get the latest and greatest gadget or make their hull look pretty every other year for example. I don't get it. I do however like the result of neglect, it puts food on my table

[RGrew176]

This will be the first time I did not change the oil as part of my winterization process. It still feels weird to me so I think next fall I will go back to changing the oil prior to winter layup.

[Mississippi Voyager]

Source of the post

Source of the post Darren, I have always run Mobil 1 15/50 full synthetic in my merc gassers. Cheaper than the merc semi, and better oil.

Why did you decide on the 15w50 ?....just curious about the grade difference, not the cost.

The one thing I like about the merc oil is the cold number......boat engines run cold and it takes quite a while to get the engine oil temp up to the point where it acts like the higher number. That said I use rotella 15w40 in everything, but it is still interesting to consider.

Mobil 1 markets 37 different variations of their Mobil 1 synthetic. Of those 37, three of them have high levels of ZDDP, which is zinc and phosphorous that are anti-wear additives. The 15w-50 is the closest Mobil 1 to correct spec for gas engines in boats. Crusader spec for oils in their manuals in the 90's was straight 40 weight. In the 2000's they changed this to 15w-40 and also recommended the same for the older engines like my 1995 Crusader 350XL's.

The vast majority of modern oils have greatly reduced their ZDDP levels because it will damage the catyalytic converters on modern cars. Some boats, starting in the mid 2000's also have catalytic converters and also should not use oils high in ZDDP. GM block gas engines up to 1995 have flat tappet cams which require high ZDDP levels (Approx 1200 PPM - Parts Per Million is optimum) to reduce camshaft wear. 1996 and later Crusaders (and Mercs) have roller cams and it is not critical to have high ZDDP oil in them. Still doesn't hurt to have the extra wear protection. But, if you have a catalytic converter in your boat, you should not use the high ZDDP oils. I personally use Rotella T6 15w-40 in my 1995 Crusaders which has 1200 PPM ZDDP and is full synthetic. (This is "New" Rotella which still has the right amount of ZDDP.)

I always like the statement I do "X" and I haven't had any problems....well...you never have any problems ....until you do!