Change oil beginning of season or end of season?

As I think about winterizing in late November or early December I am uncertain when is the preferred time to change the engine and generator oil. Both were changed in April and there is only 50 - 60 hours on the main oil and 10 on the genny. Main is a Ford Lehman 120 with 3100 hours. Do you change in November and let it sit until April or change in April? Or does it not matter?

Normal practice is to change the oil right before haulout, then let it sit over the winter with clean oil. That oil is then good for the next season. Best to change before running to the haulout so you get an hour or two for the fresh oil to spread around. Even with only 10hr on gennie oil, I'd change it anyway, it is not much oil.

Experts say to do it in the fall. Engine oil does not really "fail" it retains most of its lubrication qualities for far beyond the recommended change periods. The problem is that used old accumulates acids and other nasty residues which could damage the engine. Detergents and additives do a good job of suspending particles but sitting all winter may allow them to collect in low areas or in filters. Best to get it out and have the clean , new oil in the engine for the winter.

pete

Personally, I always change right before I winterize. Sitting over the winter with clean oil might be slightly nicer to the equipment. Plus, it's one less thing to worry about during spring commissioning.

I prefer the fall and an oil analysis to go with it.


That way you might be informed of impending issues which you now have dead time to work on.

Changing at 50 hrs and 10hrs? We don't know anything about winterising here in Australia but I find the idea of changing oil at those intervals pretty strange.

Aquabelle said:

Changing at 50 hrs and 10hrs? We don't know anything about winterising here in Australia but I find the idea of changing oil at those intervals pretty strange.

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For a lot of us who store the boat over the winter, oil changes come at either some number of hours or at the end of the season (regardless of hours), whichever comes first. And in some cases, it'll get changed 3/4 of the way through the season and there may only be another 20 - 30 hours of runtime before the end of season change.

Not sure I would bother to change it if I was expecting less than 50 hours running before the end of the season.

It is a bit strange to change oil that early. But the Lehman runs cool oil temps (sea water oil cooler) and the cool oil temps are not very good at driving out moisture from combustion. Bearings DO NOT like sitting if there is any moisture present. So a good idea to have it sit with known fresh oil.

Other engines that run 210F oil temps there will be no moisture in the oil. Those I see no problem sitting over the winter with 60hr oil.

My Cummins I generally go 300hr on the oil and in some periods where I don't run it much, that could be over two years. I'm fine with that as the oil is coolant cooled and runs hotter than the coolant. And no winter storage here in NC.

Ski in NC said:

It is a bit strange to change oil that early. But the Lehman runs cool oil temps (sea water oil cooler) and the cool oil temps are not very good at driving out moisture from combustion. Bearings DO NOT like sitting if there is any moisture present. So a good idea to have it sit with known fresh oil.

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This is a good point. A lot of gassers have seawater oil coolers with no thermostats as well. I've debated adding thermostats to the oil coolers on mine for this reason, as the oil gets warm enough when running up on plane, but stays pretty cool when running slowly and the engines aren't under a lot of load.

Pete Meisinger said:

Experts say to do it in the fall. Engine oil does not really "fail" it retains most of its lubrication qualities for far beyond the recommended change periods. The problem is that used old accumulates acids and other nasty residues which could damage the engine. Detergents and additives do a good job of suspending particles but sitting all winter may allow them to collect in low areas or in filters. Best to get it out and have the clean , new oil in the engine for the winter.

pete

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I hear this often but it seems to ignore the oil additives/ingredients that are there specifically to neutralize acids. Those that test their oil know how much neutralizing capacity remains and it has to be a lot after only 50 hrs.

"Total BaseNumber (TBN) is the measurement of the amount of these*acid-neutralizing additives*and is commonly referred to as the “reserve of alkalinity”. New diesel*engine oils*typically have a starting base number of around 10."

It is good to have adequate TBN. But that does not help much if there is moisture in the oil. It will cause pitting on the bearings.

My oil change in April was its first since I bought the boat. Changing it in November will get me on an annual schedule. Until I retire I'll average about 100 hours per year unfortunately.

Pete: it does not accumulate acids. That is a fairy tale oft repeated over and over and over again. Oil contains acid neutralizers that last a very long time, far more than what might be generated in a single season. So, change out your good oil if you wish. I don't. I test and change when the oil analysis says so. Oil is not all that expensive to most boaters, if self-changed, whiich I do but why mess with changing out 24 quarts of oil and two filters any,ore often than need be. Yeah, I know folks, cheap insurance. Using the common knowledge, why not change oil every fifty hours cuz, you know, there is acid in there eating up your engine's internals.

Pete Meisinger said:

Experts say to do it in the fall. Engine oil does not really "fail" it retains most of its lubrication qualities for far beyond the recommended change periods. The problem is that used old accumulates acids and other nasty residues which could damage the engine. Detergents and additives do a good job of suspending particles but sitting all winter may allow them to collect in low areas or in filters. Best to get it out and have the clean , new oil in the engine for the winter.

pete

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Ski, with great respect, the moisture non-issue is another bogeyman. I have tested oil many, many times and the test comes back with no water in the oil.

Ski in NC said:

It is good to have adequate TBN. But that does not help much if there is moisture in the oil. It will cause pitting on the bearings.

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catalinajack said:

Ski, with great respect, the moisture non-issue is another bogeyman. I have tested oil many, many times and the test comes back with no water in the oil.

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Moisture accumulation, like oil lifespan, is one of those things that varies based on the engine design and usage patterns. In some cases it'll be a concern, in others it's not.

I too have tested oil several hundred times. Rarely does it show high moisture in the analysis.

But there is corrosion on valve gear and pitting on bearings. That does not happen unless there is moisture in the oil.

Ski in NC said:

I too have tested oil several hundred times. Rarely does it show high moisture in the analysis.

But there is corrosion on valve gear and pitting on bearings. That does not happen unless there is moisture in the oil.

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Moisture or oil being run until it's got very little TBN left and acids are starting to become an issue.

I change mine in the fall, regardless of the number of hours on it and at 200-250 hours during the season if I have that many hours on it. We tend to use the boat a bit during the winter months. I keep a heater going in the ER, the engine sits at about 60 F, and with the dehumidifier on the boat, the ER is pretty dry.

Jim

I don’t doubt that some one in a laboratory some were could give us the ultimate answer. I doubt there is any measurable difference between fall and spring oil changes. The real difference is between those who change oil on schedule and those who don’t change oil.

Issue of oil change seems to be front and centre with all boaters. The mfg of engines sets the calendar to ensure that the engine will meet its forecasted life. The issue with moisture in oil, along with other contaminates do have an affect on a dormant engine. Considering that most boats are stored on the hard for upwards of six to seven months, that engine deserves fresh oil. As for those of us who leave our pride and joy afloat, once again many engines never are fired during the Nov-May period should follow the same advice. The engine left with dirty oil, and if diesel is the fuel the oil is full of carbon and that build can and will affect rings, valves as well as seals.


The curse to us all is the "dockstarter". He who comes to the boat and starts the engine at the dock. Lets it idle to show operating temperature then shuts her down. The oil has not really reached proper temperature notwithstanding the temp gauge reading. But what happens is you leave a warm block that as it cools creates moisture within. That moisture level will never show on an oil test but that H2O will attach itself to metal and other bits and pieces shortening their live.


Oil is inexpensive, systems to remove and replace are similarly inexpensive when compared to major engine repair. Any moderately mechanically adept boater can do the task. Follow the mfg advice, change annually, or when specific hours are attained, but nevertheless, an annual change should always be done. Set your maintenance calendar accordingly.

I hate to break it to but, your engine doesn’t know it’s the end of the season. Just change it at a proper hourly rate. In the construction business some equipment can be used for 300-400 hours then sit in the bone yard for a year not being used. There is no such thing as winter storage. 3126, 3208, 5.9 , JD’s it doesn’t matter. We charge the battery and light them up. Never ever lost an engine to oil.

End of season for sure. That's when the old oil has any acid in it.

Well, let me make sense of what everyone is saying:

Acid in oil- This is definitely a historical problem, back when diesel had 500 ppm of sulfur which when burned, formed sulfuric acid. Today's diesel contains less than 10 ppm sulfur and combined with acid neutralizing additives, it is not a problem any more.

Water in oil- Ski makes a good point- sea water oil coolers don't let the engine oil get up to proper temps to boil out any water particularly if the engine is run lightly and he has seen plenty of bearing pitting and that can only come from water in the oil.

So if you run your high output engine lightly, like I did with my former Yanmar 370 hp engine, then you probably have a bit of water in the oil at the end of the season. In this case I probably now would change the oil at the end of the season. Confession, I never did.

But if you run your engine hard and especially with a coolant oil cooler like the Cummins, then it is probably ok to wait until the hours have built up and not just change the oil because it is the season.

The worst thing you can do is start your engine once a month and run for 5 minutes in the belief that you are helping it. Unless you run it for an hour at higher loads, you are probably doing more harm than good.


David

djmarchand said:

The worst thing you can do is start your engine once a month and run for 5 minutes in the belief that you are helping it. Unless you run it for an hour at higher loads, you are probably doing more harm than good.

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Agreed. If you can't run it fairly often and get it good and warmed up and under some load (and this applies to gas engines too), better to not start it. And if it isn't going to be run for a while, fog it, change the oil and store it properly.

I change mine before hauling out in fall. I only put about 100 to 150h per season but I prefer to do it before haul out because:
1. It is not worse than doing later.
2. I will do it anyway.
3. I will have a lot of other things to do in spring before splashing so if I can check that out of my list, good!

L

For my charter boat, I always changed engine and transmission oil in the fall along with antifreeze. Did fuel filters and raw water pump impeller in the spring. Everything was done once a year whether it needed it or not. Probably less than $250 for everything. One can argue whether it was excessive or not, but a lost day on the water could be $1k loss that you don't get to make back up.

The trawler gets winterized by moving it to Florida. In the boatyard now doing annual maintenance in preparation for heading South around the middle of the month.

Ted

Cyclone... could you explain your comment
"But what happens is you leave a warm block that as it cools creates moisture within."

I get it that you can not drive off moisture if you dont run it hard to get oil temp up but
How does a warm block cooling create moisture?
Isn't that the case every time one shuts down? The engine cools.

Yeah, the issue is moisture in blowby and such condensing in the oil when the oil isn't hot enough to prevent it (and also not hot enough to evaporate it out). The block cooling is irrelevant.

Because of low hours each summer boating season I've been leaving the oil in the crankcase over one winter storage period. Last year I switched to Rotella T6 synthetic because the literature says it accumulates less contaminants and would be better sitting in the crankcase over the winter.. It certainly looks a lot better after running one season than the dino oil I used previously. Consumption also dropped. It's still inexpensive in the big scheme of things