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?

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.

Why risk it for $100 oil and filters ??

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.

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.

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.

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.

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.

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.

Later,
Dan

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.

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.

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.

Nomad Willy said:

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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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.



David

Nomad Willy said:

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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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.

CEC

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?

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.

High Wire said:

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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If the remote possibility of a filter rusting through is a concern, why not just change the filter rather than wasting perfectly good oil?

Civilitas said:

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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Here, here. Science trumps old wives' tales.

TF where else can one get 100 correct answers to the one simple question

gaston said:

TF where else can one get 100 correct answers to the one simple question

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That is what I love about this place

"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,"

Cold starts all winter is not uncommon, it is not usually a recommended procedure.

The engine never gets warm enough (gas or diesel) to burn off combustion blowby.

Changing the oil in spring is a good idea with this procedure to get rid of the combustion by products .

With most oils the additives are 15% to 20% of the oil , and one of the more important is the oils detergent.

The detergent can lift and capture the "fines" that pass thru most oil filters (bypass filters may be an exception) but in order to work the oil must be HOT and best is when it circulates for hours to lift off the fines that stick to most interior surfaces.

Its never fun to change oil after a long days run , as the Hell Hole will live up to its name , but there is no extra expense and your engine will Love you for the work.

We always hear about engines with multiple tens of thousands of hours between overhauls.
In many cases I believe it is because the oil is changed on the fly, a lever is thrown and the tank of fresh oil is fed and the tank of used oil is cut off.

This happily captures the gropsh in the old oil, fines, acid from combustion and the rest.

The best folks with 5Q or 10Gal of oil in an engine can do is good, frequent oil changes.

I have two kinds of oil filers, the standard one and a 2 micron bypass filter.
So as the engine runs, all oil is filtered by the standard full flow filter continuously to maybe 15 microns, I used a Pure One typically, and the other filter is a bleed stream bypass, so a small stream of oil goes slowly through getting cleaned to 2 microns. The output simply dumps back into the oil pan. I know it is 2 microns as I asked Fram who makes it and that is what they said. It uses stacked plates and is pushed into a steel housing

https://www.ruralking.com/fram-by-p...aMg3o4XY0-5Dx7qjaXRgFZFBayTdssXhoCNSQQAvD_BwE


It is an older design and was used on industrial and farm and marine etc... from way back in the 50's till today. Although likely today, they save money by NOT installing an extra bypass filter in addition to the full flow filters. IMO, having both is best, it does help with getting 'fines' out of oil, as it is those 'fines' which grind away metal as your main filter can not catch those abrasive 'fines'.

Another thing about oil filters, all full flow filter designs have an internal bypass, either in the filter itself, or the housing it screws onto, so that when oil is thick and cold, it can flow to the engine, otherwise the full flow filter could not flow enough oil when it is real cold. The other thing is as your full flow filter steadily clogs up, it filters more efficiently, but it can not handle the flow so well, so the internal bypass may open if it sufficiently clogged up allowing unfiltered oil to flow to the engine. That is probably why if you don't change your oil and filter, those engines more likely to grenade on you., cause the oil is dirty and the filter can not do its job. If your oil is ok, just change the oil filters, otherwise your just throwing away money changing out good oil, of course the oil companies and the oil sellers like that..

siestakey said:

That is what I love about this place

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Yes, we like to cover all possibilities here, so it is impossible to know what to do.

In all seriousness, get the oil analyzed; you will have evidence to make an informed opinion, know what to do next time, and get that info on TF.

Between science and old habits I'd rather change. If a few years has passed. A lot cheaper then a motor blown and less time to wait to analyze the oil. My pennies worth.

Thanks, all.

I will change the oil before we start. I’ve had the oil analyzed twice already—once after sea trials (when I’m sure we were looking at new oil) and again after we ran from Florida to the Chesapeake. No issues. But after sitting up this long with little use, I’ll take the more conservative route and change/analyze.

If the oil analysis is going to cost $50(25/engine), and new oil would cost $100......its like getting an oil change at half price. Its like the Mastercard commercials....."Oil change = $50, peace of mind = Priceless.

its hard to quantify, but there is a financial value to reducing the items on your list of things to worry about.

Oil is best analyzed when being changed after a long period of use.


It will then contain the iron, fuel, and the rest of the items being looked at.

I’ve recently been told, while at an engine manufacturers training course, that the typical New England temperature changes over the winter will destroy the additive package in new oil installed when boats are hauled for the winter necessitating a change upon launch in the spring even though the oil was never used. This due solely to condensation inside the motor as the temperature fluctuates. These people are only concerned with maximizing engine longevity and maintaining their reputation, they are not selling oil or oil changes.

Daveo said:

I’ve recently been told, while at an engine manufacturers training course, that the typical New England temperature changes over the winter will destroy the additive package in new oil installed when boats are hauled for the winter necessitating a change upon launch in the spring even though the oil was never used. This due solely to condensation inside the motor as the temperature fluctuates. These people are only concerned with maximizing engine longevity and maintaining their reputation, they are not selling oil or oil changes.

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Hum if true I would suspect more engine failure in boats, and cars, up here than any other country

L