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When hydrocarbon chains are broken by mechanical shearing, the products are free radicals that rapidly combine with other compounds. If oxygen or water are present, acids will form. So while shearing initially reduces the viscosity of an oil by reducing the size of the largest molecules, as the...

I think that you guys may be obsessing over nothing. The valve train is the only adjustable engine component. A little extra wear in that compartment would be off little significance with respect to overall engine life as long as the valve clearance is kept within specs . How many engines fail...

Removing the aromatics should reduce soot production, since they are more prone to incomplete combustion than the other major fuel components. However, this effect may not be realized in engines that are not engineered to take advantage of the resulting higher cetane fuel.

A marine engine siting below deck is subjected to nearly 100% humidity almost all the time. But the major difference is that boat engines typically sit for long periods of time without running, whereas automotive engines rarely sit for more than a few days at a time without being run. So the...

If a boat is stored in the water, the engine is exposed to multiple cycles of heating and cooling in an atmosphere that often exceeds 100% humidity. Thus, condensation on metal parts, particularly in the valve train area, is a real consideration. The net result is not so much water accumulation...

There is no such thing as a bad CI-4 rated oil for the ISB. All of the non-synthetic oils are very similar. Delo uses the most oxidation resistant base oil and has somewhat better low temperature flow properties than the other 15W-40s. But the differences are probably not relevant. As Jelly...

I have a 1998 90 hp Honda outboard that sits for months at a time. I change out the M1 10W-30 at 18 month intervals and the oil analysis is always excellent. Never more than 8 ppm iron and strong TBN. Total hours are only 50-75 per 18 month interval. I've learned to stop worrying.

Anyone who thinks that they can predict the final HTHS viscosity of a blend (this is what really matters) based on the virgin properties of the starting oils is fooling themselves. The point not being considered is that the final viscosity of a blend is primarily influenced by the longest (or...

That's a hypothesis, but not a null hypothesis. A null hypothesis would be that there will be no significant difference between the wear metal accumulation among the 3 oils. Like most other "experiments" proposed and conducted on this board, you will not be able to conclude anything meaningful...

You should do an oil analysis to convince yourself that once a year or 7-8K is fine. The only problem you might run into is fuel dilution from short trips. Believe your own data rather than what other people will tell you. For what it's worth, I change once a year with the same oil and engine...

Oils with weak detergent packages require less base to reach a given TBN. So the base available to neutralize accumulating acids gets depleted faster than in an oil with a stronger detergent package that requires lot of extra base to get to the same initial TBN. The detergent acts like a buffer...

The things you need to understand in order to make sense from all this are: 1) The detergents in the additive package are weak acids. So a well fortified oil starts out with a relatively high TAN value right out of the container. 2) A strong detergent package requires more total base in order...

Why? Do you think a filter change would improve this UOA result? Looks like he has a wining combination here. Changing the filter and adding a quart of oil would just be a waste of money. Believe the data.

You can use standard marine anti-corrosion wheel bearing lube for all of the applications except #1 and #4. Pull the prop and re-lube each year. Mercury dealers sell several type of lower unit lube for #1. The names have changed over the years. You should ask the dealer which one is appropriate...

Anything that isn't made of hard steel (bushing for example) are considered white or soft metal. GL-5 lubes have about twice the level of ZDDP, etc. than GL-4. High levels of anti-wear compounds can attack soft metals and accelerate corrosion. Most GL-5 lubes are now tested for soft metal...

You guys really need to read Gao et al, SAE 2003-01-3119. ConocoPhillips and Ford engineers tested 5W-20 oils with different levels of ZDDP using a laboratory valve train bench test that employed constant monitoring of a radioactive tracer embedded in the metal as well as wear scar measurements...

You can generally mix any lithium complex based wheel bearing grease without a problem. However, you should use a marine grease, rather than a general purpose GL-2 lube in boat trailer bearings because the marine stuff has better corrosion inhibitors and generally a higher drop out point. Also...

Ded's answer is incorrect. TBN is an absolute number that is a determination of the amount of residual acid neutralizing capacity remaining in the oil. Oil with a TBN of 1 is no more corrosive than oil with a TBN of 12. The problem is that when TBN reaches 0, things go down hill very fast with...

The problem is that the OMC 100:1 tests were conducted at the bench,probably with engines running under constant load and using freshly mixed fuel. There were lots of engine failures in the field. Reality sets in when you add variables such as stale or poorly mixed fuel, poor planning hulls...

PAOs used as lubricants are typically branched chain molecules. As such, inter- and intra- molecular interactions can occur. Only inter-molecular interactions (between molecules) contributes significantly to viscosity (unless the molecules are very long). At lower temperatures, interactions...