Diesel oil change question

[giantfan]

I am new to the whole diesel game and have a question about when to change my oil.

My question is about the adverse effects of changing the engine oil in the spring rather then the fall. I usually come out of the water in the beginning of Nov and go back in the water in the beginning of April. From reading in some of the other threads I see that a lot of people change their oil in the fall as a diesel motor produces some sort of acid that is hamfull to the motor. I have also heard that even fresh oil laying in the pan is subject to absorbing moisture over the course of the winter layup.

Is it better to start the season off with a fresh oil change and avoid the possibility of running with moisture contaminated oil, or will the acids be that corrosive to the motor that it sould warrant changing the oil in the fall during the winterization process?

I have also been told that the only thing that is in constant contact with the oil is the oil pan and the pickup for the oil pump???
If this is in fact the case, what are the acids in the oil doing to the motor? Is it really the oil pan that they are doing damage to? I haven't heard of anyone having their oil pan rot out from the inside (just because I haven't heard of it doen't mean that it doesn't happen)

Just trying to do the right thing by my motors.

[Russell A. Jost]

GF, My manual says to change the oil every 250 hr. So I do it every 125 hr. and always just before layup. Otherwise, I would only be changing it once a year, which seems like a long time between changes to me. The oil is a hell of alot cheaper than a rebuild.

[giantfan]

I hear ya... Last year I changed it in the middle of the season with only around 75 hours on it.

What I am really getting at is....should I do it in the fall or in the spring. My concern is that if I do it in the fall I may get some moisture in the oil over the winter from condensation, which I will be running until I change it in mid season.

Which is the worse of two evils? Risk the acid problem (which I don't know what kind of problems this will bring) and have fresh oil in the spring or risk the moisture problem and do it in the fall?

Why do you do it before layup and not in the spring?

Thanks for the reply.

[southshore30]

The contaminants in the oil are from the diesel fuel and carbon from the combustion chamber due to the high compression ratio of a diesel engine. Also, you are circulating all of the contaminants around in the older oil, change it out so those sediments don't get a chance to sit in your oil pan for 6 months and form a layer of grunge. Yes, it is definately best to put her away with fresh oil run through the engine just before running the antifreeze through the raw water system. New oil sticks to the engine parts much better than the older thinned out contaminated oil over the course of the engine sitting. Any condensation that may have gotten in to the oil or engine will steam off when you fire it up and get her hot the first time in the spring.

[Russell A. Jost]

Two of our local diesel engine mechanics told me it should always be part of the layup/ winterization process. My engine compartment is dry and heated to 45 deg. in winter. I close off the air intakes with velcro and plexiglass panels so condensation is not an issue. Rust and corrosion is almost none existent. I know it sounds a bit overdone but thats just me.

[seapower]

This is one of those question's where you get answer's split down the middle either way. Let me first say that oil and filter's are the cheapest "insurance" you'll ever buy for your boat. At winter lay up customer's will go both way's. What I will strongly suggest to you is, in the spring BEFORE you start your use, get a FULL SERVICE done to your engine. This change's oil & filter's,primary & secondary fuel filter's, belt check, impeller check, transmission oil change,valve adjustment, zinc's, air filter, alignment (if applicable), etc... I know this may sound like alot, but if done as a ROUTINE, it takes part of a day at most. The positve side of this is ,it will help you to have a problem free fishing season. The key is take care of it before you have a problem. By the way if you can't make up your mind when to change you oil, change it when it is winterized and at the spring full service. It's still pretty cheap peace of mind. The old rule of thumb on diesel oil change interval's was every 200 hour's or once a year, which ever came first. Again check your owner's manual, it will have your maintainence schedule's in there. Some engine manufacturer's actually suggest changing oil more frequently. Check it out according to the engine that you have, you won't be sorry. Frank,SeaPower

[giantfan]

Thank you Frank...

Last year I did all the things you listed and am planning on doing it every year.

My buddy who owns the marina where I keep it for the winter is an outboard/ IO mechanic and he recommend that I do my oil change in the spring.... I told him that I have seen that it should be done before the layup. He was the one that brought up the moisture issue and claimed that there really isn't anything sitting in the oil that that the acid could damage.

He is not a diesel mechanic and that is why I was asking the question. Doing a change at both the fall and the spring would be a win win situation but I am..... lets say cheap.... and didn't really want to throw out oil that has only been used for an hour or so.

Since you don't seem to have a strong opinion on either one.... I think I will stick with the spring to change the oil. I just got worried when I saw posted that it is very bad to keep used oil in the motor for the winter due to the acid. The oil that is in my boat right now only has around 50 hours on it.

Thanks to everyone that has replied.

[seapower]

Even if you do throw out the oil, how much money have you "thrown" away? The oil that you throw away will have any moisture present from codensation from the winter. That condensation will cause rust inside the block, giving you high iron content reading's in an oil analisys. You can use that "old" oil as a flush before your spring service. Just a thought. Repairing them is alot more expensive than maintaining them. Frank,SeaPower

[giantfan]

Even if you do throw out the oil, how much money have you "thrown" away? The oil that you throw away will have any moisture present from codensation from the winter. That condensation will cause rust inside the block, giving you high iron content reading's in an oil analisys. You can use that "old" oil as a flush before your spring service. Just a thought. Repairing them is alot more expensive than maintaining them. Frank,SeaPower

Point taken....

Would it be ok to use a lesser quality oil then what I normally use for the winter layup since I won't be running the motors with it except to get it up to temp so I can change it? What about the filters? Leave the old ones on for the winter and put the new ones on in the spring?

I forget the name of the stuff my diesel mechanic told me to use.... if I remember correctly it starts with an I.... I have a jub in my boat and I will check what it is.... but I remember it being pretty costly. I have Cummings motors.

[seapower]

I'm having a hard time getting you not to be "cheap" as you called yourself. Just how much do you have invested in those Cummin's engine's anyhow????? And your still letting phrases like "cheaper oil and filter's" come rolling off your lip's!!! You're starting to sound like a SailBoat owner!!! Boy I know that hurt, but do you get my drift??? On the Cummin's Product's I service I only use one brand of oil and filter's, guess what they're not cheap, they're good. Frank,SeaPower