Boating Magazine - Oil expert advice

[paulswagelock]

This month's boating magazine had a Q&A topic about oil. A reader asked why the used motor oil in his boat came out darker than the oil in his friends boat.

I will shorten this, but the expert's answer was because Conventional oil is dirtier than synthetic right out of the bottle, and that synthetic oils clean better than conventional.

I would say not much 'expertise' in his answer.

 

[Donald]

I read the article last night and your synopsis of the article is not very accurate.

 

[BobsArmory]

link?

 

[paulswagelock]

Originally Posted By: Donald
I read the article last night and your synopsis of the article is not very accurate.


Can't find a link.

...and I quote:
" The boat's previous owner probably used regular oil, which is dirtier.
The synthetic has more detergent in it and cleans an engine. Your buddy's oil likely looks better than yours, again a bet, because he used synthetic all along and thus it never got dirty inside the engine"

... end quote.

I believe I summarized it fine.

I suggest his buddy's looks better for some of these reasons, and none of the reasons above:
carb engine versus fuel injected, colder water temperatures during operation resulting in longer warm up times, colder ambient temperatures resulting in longer warm up time (rich running), extended idle times, different parameters (more / less WOT operation), spark plug condition, recirc loop condition, propeller match to engine rpm/load, total operating hours on the engines, size of the engines in relation to boat size.....

I do not know any of the details as they were not provided, but somewhere in this list, and I am sure there are other factors, lies the answer. It is not that conventional oil is dirtier and synthetic oil cleans better. Those are generalizations and not factual based on the details given.

 

[Ramblejam]

Originally Posted By: paulswagelock
The boat's previous owner probably used regular oil, which is dirtier.


"In simple terms, the difference is that synthetic oils are made using more advanced refining processes, and hence are of a higher purity and quality than the conventional mineral oils."

"Conventional oils also contain much greater amounts of impurities, such as sulfur, reactive and unstable hydrocarbons, and other undesirable contaminants that cannot be completely removed by conventional refining of crude oil."

Even if we look at the deposit control aspect of "dirtiness" (page 12), Mobil 1 comes in 90/100, whereas the semi-synthetic is at 49/100.

So, yes -- conventional is dirtier than synthetic, regardless as to whether or not you're looking at composition or results from actual operation.

Originally Posted By: paulswagelock
The synthetic has more detergent in it and cleans an engine.


"To test the cleaning power of Mobil 1, researchers tested a European performance vehicle and an American vehicle that had been run with conventional oil, then switched to Mobil 1. After 14,000 miles of driving with Mobil 1 at the recommended oil drain interval, the European vehicle returned to near new levels of cleanliness. The American vehicle experienced even greater improvements from Mobil 1. After the equivalent of tens of thousands of miles of sludge build up, the camshaft hold downs were many times cleaner after regular oil change intervals with Mobil 1. The rocker covers were also much cleaner after running Mobil 1."

The definition of "detergent" as used by the Boating Mag author is unknown, but they're still fundamentally correct.

Originally Posted By: paulswagelock
Your buddy's oil likely looks better than yours, again a bet, because he used synthetic all along and thus it never got dirty inside the engine


"Some of the engine tests we run simulate extremely severe conditions. This particular engine test measures oil thickening and piston deposits in simulated high speed driving in very hot weather. Oil temperature reached 150°C for 100 hours. Mobil 1 can help keep your engine cleaner under high temperature conditions.

Reference not only the "deposit control" I quoted early, but "piston cleanliness" (same page 12) as well. Again, the author is correct.

http://www.exxonmobil.com/AP-English/Files/about_who_Mobil1_supersyn_eng.pdf

 

[paulswagelock]

Your response is correct, if we were talking about the oils you mention.
We are not. This is a specific conversation about mercruiser oils, not Mobil 1.
Mercruiser synthetic is a crude based synthetic, 99% or so. Yes, it likely is hydrotreated. However, it is anecdotal at best to say it is cleaner than their conventional oil, and a gross generalization to say it I has more detergents. That is my point. The author passes along generalities as factual expert evidence.
I have had multiple samples analyzed of both mercruiser oils over the years. No, it does not have significantly more detergents than the conventional, in fact about the same within lab accuracy.

So your data might be accurate, but not relevant to the authors responses. I have been boating for 30 years, have had many, many boats, have been hands on for all of them. The causes I listed are significantly more related to the engine oil dirtiness than the expert advice offered by the author. If he made the statements as generalities and then listed other likely factors like the ones I mentioned, then I think his response would have been valid. Not as written.

..and I accept I did not qualify he wrote specifically about mercruiser oils in the original post, so I understand your viewpoint.

 

[Bror Jace]

If you look at used oil from a used engine and it looks dark, there could be a dozen different reason for that ... and semi-ignorant statements from that magazine aren't helping anyone.

The letter/article should have started off something like this:

"There are a lot of reasons why the oil in your used engine is very dark, but there are a number of things you can do to ensure your engine runs cleanly and efficiently for years to come ..."

 

[fdcg27]

This is what I was thinking.
There are so many possible explanations for oil draining darker from one engine than another.
Some oils are simply darker when virgin and this has nothing to do with impurities.
It may be a case of one engine being cleaner than another as a result of the oil used over its life, but that is no more than uninformed speculation.
It's equally possible that the engine with the lighter colored oil simply wasn't run for as many hours or that the oil used had a very weak detergent/dispersant package and much of the stuff that would have darkened it remains in the engine.
Unless you compare two identical engines run for identical hours under identical conditons using identical oils, you simply can't draw any meaningful conclusions from the relative darkness of the drain oil.