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Old 02-03-2018, 05:51   #16
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Re: Oil Change Frequency

Dockhead has the answer! The acid created in the blow-by kills the oils lubricating capacity.

I tend to change oil earlier than recommended. I buy filters by the case (3 engines with the same filter) and always carry 3-5 gallons of oil on-board that way the drama associated with doing the work is down to my ambition level.

Oh, and I created a reward system, always finish an oil change right before happy hour!
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Old 02-03-2018, 07:14   #17
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Re: Oil Change Frequency

And really, why cheap out and skip changing the filter?
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Old 02-03-2018, 07:18   #18
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Re: Oil Change Frequency

Originally Posted by malbert73 View Post
And really, why cheap out and skip changing the filter?
One reason might be to avoid the dry start, which can't be good for the engine. On the flip side, the filter contains a lot of dirty oil and just dirt. I don't know which of these factors is more important, but FWIW, I do change the filter every time.
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Old 02-03-2018, 10:39   #19
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Re: Oil Change Frequency

The best way to judge the life of engine oil is with oil tests. After a few tests after 200 or more hours will tell the story. I've experimented with extended oil life all my adult life. I did it looking to extend engine life and mainly to slow down the natural wear in bearings and especially in the bores and rings.
In the process I've used many added on bypass filters. Some that worked 50 years ago, don't work now. I guess due to changes in oil, fuel and engine design. What I've read and found is that the slower oil passes thru a filter, the more dirt and smaller particles it traps. If you closely inspect filters or cut open spin on filters, you will find in a normal cycle, they will also trap about 1/2 to 1 ounce of water.
Many 4 cylinder and smaller engines with a spin on filter can take a longer filter. A lookup of thread size and filter gasket diameter will show other filters that fit. Oil moves thru the filter slower and traps more dirt and water.
Almost any bypass filter made for over the road trucks will extend oil life on a marine diesel. Probably double, but test the oil.
I use a stand alone centrifuge now. I haven't changed my oil since 2011. I test once or twice a year. I have Detroit mains that burn a small amount of oil. The oil I add has kept the additives working and the oil is semi transparent.
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Old 02-03-2018, 14:39   #20
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Re: Oil Change Frequency

Wow, Lepke, that is really serious oil care! Good on ya.

We have a Nanni, a marinized Kubota 43 hp. Jim changes the oil and filter, and transmission ATF, guided by the manufacturer's recommendation, which is every 200 hrs, and he is of Tellie's school. Giving the machinery oil and filter changes is the least expensive way of keeping it all running well. We often do it earlier than the 200 hr. interval, so that we don't unintentionally exceed it. This engine takes 9 liters per change. And we have good reliability with our normally aspirated tractor engine.

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Old 03-03-2018, 22:16   #21
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Re: Oil Change Frequency

Originally Posted by JPA Cate View Post
Giving the machinery oil and filter changes is the least expensive way of keeping it all running well
I bought a Nissan Sentra new in 1988. The dealer set the car up for highway driving, so it took mid-grade gas and delivered 38 miles per gallon.

I changed the oil myself, twice as often as the manufacturer recommended and, while the manufacturer recommended 10W30, I used Kendall HD30.

Ten years later the car had 456,000 miles <--not a misprint) on it. While the oil had its yellow bloom for the whole interval between oil changes in the beginning, in the end the oil turned black immediately and did not require topping up between changes. Then somebody smashed into the right front fender and a great pile of rust fell down underneath the car (this was in the southern Ontario, Canada rust belt where the roads are salted in winter) and the car was Done. That car didn't owe me a thing.

The trouble free longevity was due to the short oil change interval (oil wears out) and the Kendall HD30 oil.

Just sayin'....


(You have to remember your high school chemistry.) The significance of the Kendall oil is this: In all the world all the oil fields produce straight chain carbon (aliphatic) oil. There are two exceptions, that produce oil molecules with benzene rings (aromatic). One is a small oil field in Russia and the other is the small northern Pennsylvania oil field. Both oil fields are long depleted, but if you drive through the Pennsylvania oil field, rarely you will see the giraffes in a farmer's field working. They let the oil rest for a few years so the oil seeps into the void, and then pump it. That oil goes (went) to the Kendall refinery nearby.

In the hostile environment inside an engine, benzene ringed oil is harder to break down than straight chain oil. So it lubricates better. The Kendall logo is a hand with two fingers in a V, meaning you'd get twice the mileage between oil changes. And the significance of using HD30 instead of 10W30 is, 10W30 is more convenient but to do that it contains more detergent than HD30, which is what makes it multigrade; but the lubrication of that detergent is inferior. I wanted the lubrication of as much of the gorgeous aromatic oil as possible.

And when I changed the oil twice as often as the manufacturer recommended, it lubricated that much better. Oil wears out. Oil changes are relatively cheap, compared to a worn out engine.

Incidentally, we're told that that Pennsylvania oil field is where Pennzoil, Quaker State and others made their reputation, but they've long since changed to aliphatic feedstock. And a couple of years ago a major oil refiner bought the Kendall refinery, closed it down and is now blending the small stream of Pennsylvania crude into his aliphatic feedstock; he still sells Kendall branded oil.
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Old 04-03-2018, 00:13   #22

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Re: Oil Change Frequency

Oil tests to determine when to change the oil is a waste of money. They cost more than the oil. Our small diesels don' take much oil so it's really cheap to change it. Big diesels in trucks take over 10 gallons of oil so it may become beneficial for them. Your engine probably wont wear out if you follow the manufacturers suggestion. For the vast majority of sailboats that's once a year at the end of the season. Time, not hours will be the limiting factor.
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Old 05-03-2018, 15:32   #23
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Re: Oil Change Frequency

Originally Posted by transmitterdan View Post
The only reliable way to come up with your own oil change protocol is to perform oil analysis regularly. Big trucking companies use oil analysis results to guide them in setting oil change intervals as well as other engine maintenance scheduling..

This! We do this as well. They are pretty good at setting guidance and it doesn’t hurt to have an extra set of eyes watching your engine for issues.
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Old 05-03-2018, 23:38   #24
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Re: Oil Change Frequency

It's cheap insurance.

They will pick up a trend change normally well before you will.

The increase in cerain elements in a sample will normally steer you towards the distressed area of the engine or transmission allowing targeted rectification before failure.

Much better than waiting to hear a bearing or other component beating itself to death.

Cheers Tom
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enc, oil, oil change

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