How Often Should We Change Our Diesel Oil

[Irish Mist]

On Irish Mist I faithfully change my Diesel Engine Oil once a year usually when laying boat up in the fall even though I only do about 50 hours a year. Ten years ago I had my Westerbeke 4-107 taken out to repair gasket leaks on pan. A check of bearings showed they were just as good as new with 2,000 hrs on engine. So maybe I am doing the right thing.

What do you other Dickerson Owners think about oil changes.

As background you may be interested in the following discussion from Sportsfishermen.com

Diesel oil change question

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 pick up 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.
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.

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.
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.

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.

GiantFan

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

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.

Do The Math,

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

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