Changing Engine oil Before Storage

[BonBini]

I haven’t posted in awhile and recently read some comments on “engine oil before storage”

Back in the day when I was schooled on engine oils. The key functions were to Clean, Lubricate, Cool and Protect.

Protection was from harmful acids. As it was explained to me: A byproduct from diesel combustion was sulfur. When the sulfur combined with moisture in the oil it was then Sulfuric Acid. This Sulfuric Acid was corrosive to the soft internal metals within such as bearing babit. The TBN “total base number” was the oils ability to neutralize acids. Maintenance intervals were based on 250 hrs. Engine oil capacity was engineered around fuel consumption to maintain the oils TBN within the manufactures maintenance interval. Some engineers gave there engines plenty of oil capacity while others fell prey to marketing to cut costs, weight and installation dimensions.

Today with the low sulfur fuels I question the need…. I’m not a Chemist so I don’t know what if any other acids could be present if not for sulfur.

Like to see comments on this…

I feel times are a changing

 

[Turtlesboat]

Hey bonbini, long time no see.

 

[Henry Boyd]

I'm not a chemist either and don't know whether low sulphur means no sulphur, or just less sulphur than older formulations. In any event, moisture is still a by-product so the idea of letting oil containing water, the products of combustion, and bits of burned oil sit in the engine over the winter, is just well,.. repulsive.

Since a clean filter and oil is not going to cause any problems during storage, and the jury still seems to be out on storing the engine with dirty oil, and the oil is going to be changed any way, I'm going to continue to do it in the fall regardless of the low/no sulphur discussion.

Henry

 

[paulswagelock]

Your description is accurate for oil's purpose. A few additional considerations: how many hours of use on the oil, ethanol in the gas (really important factor), carb or fuel injection, storage temperature for the boat, salt or fresh water, freshwater or closed cooling.

All of these items will also weigh in on the best practice. If the oil is going to be changed, and it is just a matter of before or after storage, why risk it? It will never hurt to change it prior, but could potentially damage internals not changing it. Ethanol in the gas wreaks havoc on oil if present, causing it to gel up. This is worse for carb engines as fuel dilution is definately present in the oil. Tbn values have dropped significantly with modern oil formulations so they just can't handle the acids as well. Small leaks with coolant or salt water will trash an oil quickly and cause it to form sludge and deposits. There are so many potential issues that I always change it prior to storage, but I am low risk tolerant.

 

[BonBini]

My original thoughts were towards diesels. I always felt they were more at risk due to the sulfur thing.

Moisture: With today’s diesel fuels it would seem the gas engines are more at risk due to there cooler internal temps. With that said, one would think that volatile burn off would take care of the normal moisture absorption phenomenon experienced during cool down. More so in a hard working boat engine as apposed to my empty truck.

My thoughts on the ethanol laced gas: as the oil becomes normally contaminated with raw gas from cylinder wall wiping, seems like volatile burn off here too should take care of the lighter ethanol, either’s and all the other lighter fuels blended in just has it has done before the ethanol craze.

Not a chemist but I do mix alcohol with pleasure

Just doing a bit of rambling in the off season. I should get back to working on the house but it’s too damn cold!

 

[sbw1]

No chemist either but a creature of habit. The conventional wisdom lines up with the advice in the manual. My hours are similar to the manual so I start and end with clean oil.

 

[Southpaw II]

I'm a gas boater, but because of where I live, I am able to crank my boat at least weekly during the colder months and let it run to temperature. Weather permitting, I get it out on the water a few times a month during the winter months. For me, oil changes occur about every 2 years, or about every 100 hours. My oil looks pretty good when I change it.

If I pulled my boat and stored on the hard during the winter, I would change the oil prior to doing that.

Don

 

[carterchapman]

We are on a small lake, so we only get 35 - 50 hours a year. My engines and genny take 5 gallons of oil, so $200 of oil and filters each fall are real cheap insurance for $25,000 worth of engines...