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Old 05-22-2018, 06:27 AM   #1
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Does lightly used oil deteriorate over time?

I last changed the oil in our Lehman 135s in 2015, using Shell Rotella. Since then we have put under 20 hours on the engines because we have been working on the boat extensively during this period. We are getting ready to take a long trip this summer. Should I change the oil again or is it still probably OK to use?
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Old 05-22-2018, 06:38 AM   #2
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It's probably fine, but three years is pretty long. And it depends on how you ran those 20hrs. Lots of idling and short trips the moisture builds up, and Lehmans are known for running the oil rather cool.

If you bothered to ask, that means you are a bit concerned about it. I'd change it even if only for the peace of mind.
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Old 05-22-2018, 06:47 AM   #3
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Why risk it for $100 oil and filters ??
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Old 05-22-2018, 06:54 AM   #4
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I would change it....some might not bother with the filters...but again for the total cost.....I would change it all.

most all literature discusses age as well as hours and 3 years exceeds every recommendatiokn I have ever read.

for those where it does cost a lot or is inconvenient, a $20 analysis might be a possibility.
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Old 05-22-2018, 07:53 AM   #5
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The oil itself won't break down, after all it is millions of years old (unless you use synthetic). However, the additives could deteriorate and the oil will pick up moisture and become acidic. I would look at it by pulling the dip stick and wiping it on a white paper towel. If the oil looks new you are likely good to go. If it is black (carbon accumulation) a change would be a good idea.
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Old 05-22-2018, 09:05 AM   #6
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Give to me, and I will use it in my car.
Oil if well filtered lasts a very long time, the additives they add to oil if the oil is used heavily can wear out. You can not tell just by looking at the oil if it is bad. It might look bad but still be ok.

I have one Saturn Sl2 I rebuilt and typically run used motor oil from mine and others cars. I have now 100000 miles on the rebuild and still runs great, good power and no significant oil use. I have 248,000 miles total on that car.

Fuel dilution can ruin engine oil, you dont want to use that in your engine. That you can usually tell. That would be oil coming from a poorly running engine.
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Old 05-22-2018, 09:55 AM   #7
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With a free breathing crankcase, oil will absorb water from the air. If in a high moisture area, I might have that concern. I would do a simple crackle test to get a coarse view of free water content.

water in oil does cause accelerated metal wear.

3 years may not be "long" where I live now, but in some areas of the world it could be significant.
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Old 05-22-2018, 10:09 AM   #8
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Exactly,, we are all guessing.... so without any reasonable scientific testing there are 2 choices....gamble or change.

A possible 3rd is wait, but change after a shorter interval or an analysis.

There most likely would be minimal damage or wear if only used only for a short time if the oil had dropped below specs.
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Old 05-22-2018, 11:17 AM   #9
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The only way to know is to do used oil analysis but the cost of the test might be as much as an oil change. I left oil in my tractor for three years once by mistake. The oil test said the oil was fine when I did change it.

If it was me, I would test the oil because I like to know what is going on, and change the oil.

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Old 05-22-2018, 11:36 AM   #10
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No question in my mind change the oil and filter. Brand new no it doesn't break down, but once it mixes with old residue yes it starts to break down. That's not to say it is worthless and it will instantly kill your motor, but on my boats if the oil was replaced and the motor started then the oil change clock starts as well. 6 months is max for me then its change time. If I'm not running the boat over winter I wait and change it before I do plan to use it. Oil R&R is cheap compared to what it cost to ignore it. Most rebuilders will tell you every 150hrs or 3 months during warranty periods.
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Old 05-22-2018, 04:19 PM   #11
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As long as the oil is clean and tests ok, it's ok to use. I centrifuge my oil and test once a year. I haven't changed oil since 2011, just add make up oil. The filters get changed once a year because they will gather some water (usually a few drops) and I cut my filters open to check what particles they're catching.
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Old 05-22-2018, 05:18 PM   #12
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Oil “breakdown” is not from physical abuse in this case. Moisture from condensation and the air along w other chemical degradeations that I have long forgotten the details of do apply to situations such as this.

Change it IMO but the small amount in the filter is fly stuff especially if the filter is small re the quanity of oil. I had a remote mounted filter that was twice as large as the OEM filter. Changed filter every other time. Now I’m back to using the OEM filter (small) so I change filter every time.
Warm up the oil to operating temp to homogenize the particulates and the moisture. Most all the chemicals will disperse themselves in the oil and go bye-bye when you pull it out.

Boats that are routinely laid up during the winter usually get an oil change in the spring. Frequently the oil never gets run in the engine but it should for a very short time just to pump it everywhere oil goes. The new oil in the fall oil change (just before lay-up) helps protect bearing and other metal surfaces during the winter. Seems like a waste but it’s a fairly standard procedure in boat yards.
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Old 05-22-2018, 06:27 PM   #13
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Quote:
Originally Posted by Nomad Willy View Post
The new oil in the fall oil change (just before lay-up) helps protect bearing and other metal surfaces during the winter. Seems like a waste but it’s a fairly standard procedure in boat yards.

I just had this debate with the guy who was surveying my boat prior to sale. I told him that was an old principle, to change oil every season, that may have had some validity when sulfur content of diesel fuels was high, but not any longer with ultra low sulfur diesel.


He sort of agreed with me, but as a former service manager of a marina he said that making money takes precedence over logic. I truly believe that much of all marine service work is done for only this reason.


Oh, and ask me about the fuel polishing that he recommended be done.



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Old 05-22-2018, 07:05 PM   #14
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Quote:
Originally Posted by Nomad Willy View Post

The new oil in the fall oil change (just before lay-up) helps protect bearing and other metal surfaces during the winter. Seems like a waste but it’s a fairly standard procedure in boat yards.
Is this fall change for diesel motors only or Gas motors as well? I’m asking because I have both types and curious as my gas boat is the one that sits durring winter. I can buy it for the diesel due to fuel, but have trouble thinking it would do much for the gas. If the oil has water in it there’s other issues just used oil seems ok. I can’t think of any other way the oil due for a change and just sitting in the bearings in a film would do much damage?

I will say that if I don’t use my gas boat in the winter I will still run it for a few minutes every 4-6 weeks during that time. Thinking I’m keeping it heathy doing that, so if winterizing with fresh oil is a standard procedure, I might start. Interesting info I haven’t heard so thank you.

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Old 05-22-2018, 07:47 PM   #15
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My vote is do a full change. Let’s say there is one drop of water that separated out of the oil in the filter can. After sitting in place for months the drop corrodes the inside of the filter can half way through. Then you come along and do a cold start. What if the can pops a hole and pumps several gallons of lube oil all over the engine room and trashes your engine. Was saving the hundred bucks worth it?
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Old 05-23-2018, 01:09 AM   #16
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The smart move is an oil analysis, which is cheap, easy, and definitive. And what you learn from it can be very valuable for the future.

Test one engine now; run the engine to temp (if it has not been run in a while), then let it cool and sample it. $25 and a few days for the results. You will learn about the health of the engine and the oil, and then be able to decide intelligently. You will get useful data points on wear, water, coolant leaks, air filtration, etc. Odds are 99% it will come back with a very clean bill of health, as a number of multi-year samples with modern oil I have seen have come back. If it doesn’t, you’ve likely discovered something important.

Presuming it comes back clean, you can then decide how long to run the oil. And when that interval is up, you can sample the other engine. You will then have a test of how oil holds up in your engines, what a future change interval should be - very likely longer than you are doing - and also the health of both your engines.
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Old 05-23-2018, 01:53 AM   #17
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Old 05-23-2018, 03:03 AM   #18
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My vote is do a full change. Let’s say there is one drop of water that separated out of the oil in the filter can. After sitting in place for months the drop corrodes the inside of the filter can half way through. Then you come along and do a cold start. What if the can pops a hole and pumps several gallons of lube oil all over the engine room and trashes your engine. Was saving the hundred bucks worth it?
If the remote possibility of a filter rusting through is a concern, why not just change the filter rather than wasting perfectly good oil?
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Old 05-23-2018, 03:05 AM   #19
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The smart move is an oil analysis, which is cheap, easy, and definitive. And what you learn from it can be very valuable for the future.

Test one engine now; run the engine to temp (if it has not been run in a while), then let it cool and sample it. $25 and a few days for the results. You will learn about the health of the engine and the oil, and then be able to decide intelligently. You will get useful data points on wear, water, coolant leaks, air filtration, etc. Odds are 99% it will come back with a very clean bill of health, as a number of multi-year samples with modern oil I have seen have come back. If it doesn’t, you’ve likely discovered something important.

Presuming it comes back clean, you can then decide how long to run the oil. And when that interval is up, you can sample the other engine. You will then have a test of how oil holds up in your engines, what a future change interval should be - very likely longer than you are doing - and also the health of both your engines.
Here, here. Science trumps old wives' tales.
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Old 05-23-2018, 03:31 AM   #20
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TF where else can one get 100 correct answers to the one simple question
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