Diesel Engine Oil Change Frequency?

[Kenomac]

I know this has been discussed before, but I'd like to put a new angle on it. Here I am hunting down the appropriate oil for my Yanmar 100hp turbo diesel and Westerbeke 10kw generator at the end of the season.... and wondering if it's even necessary to change it? Here in the Adriatic for six months, we covered about 1200 NM, but having installed a 450w solar array and basically sailing most places on new sails, we've hardly used the engines.

Only 100 very easy hours on the main engine and maybe 60 hours total on the generator. Do I even need to change the oil this season, or can I let it go for another year? Seems like a waste of good oil, neither engine burns any. We didn't even go through a full tank of diesel (less than 225 gallons).

What do you think? Geez... I just realized I haven't changed the oil in my diesel Bobcat for eight years... and it gets more hours than my generator, and runs perfectly all winter long... in below freezing temps.

And if I do decide to change the oil, is this stuff OK for the Westerbeke generator? Nowadays, most oils on the market here in Italy seem to be formulated for all engines diesels included, and most are synthetic.

[Drew13440]

Change it. Motor oils and additives start to breakdown with about six months of use and start to become pretty nasty, even acidic. It's probably too late for the Bobcat...

[Kenomac]

Originally Posted by Drew13440

Change it. Motor oils and additives start to breakdown with about six months of use and start to become pretty nasty, even acidic. It's probably too late for the Bobcat...

The Bobcat probably won't know what to with new oil.

My uncle had a Ferrari Testarossa for 20 years, never once changed the oil. Just kept adding Mobile 1 synthetic and spun on a new oil filter when he remembered. No problems in over 200,000 miles in that car. Really makes you wonder about all the warnings.

[rwidman]

Didn't your engines come with owners or service manuals? Can you get them on-line? How much are these engines worth compared to the cost of oil and filters?

The engine manufacturer knows the requirements better than anybody. Follow their recommendations.

[Kenomac]

Originally Posted by rwidman

Didn't your engines come with owners or service manuals? Can you get them on-line? How much are these engines worth compared to the cost of oil and filters?

The engine manufacturer knows the requirements better than anybody. Follow their recommendations.

Yeah, The service manuals recommend I have a Yanmar service tech do the work using official Yanmar oil. The engine is 16 years old, way outta warranty, so that isn't going to happen.

Yours truly has been the service tech for the past 7 years.

[MarkSF]

Originally Posted by rwidman

Didn't your engines come with owners or service manuals? Can you get them on-line? How much are these engines worth compared to the cost of oil and filters?

The engine manufacturer knows the requirements better than anybody. Follow their recommendations.

The manual for my Universal 5424 is now 33 years old. In that time, diesel fuel has gone from high sulphur to ultra-low sulphur, and engine oil from straight grade dino oil to multigrade with new options like synthetic, and semi-synthetic.

It's entirely appropriate to discuss this issue.

With a modern synthetic oil, I wouldn't worry too much about stretching out the engine hours a little, after all, most cars (including diesels) now run 10,000 mile intervals, which is equal to about 200 hours. However, they also require at least yearly changes.

My Universal gets oil changes every year, and it's done maybe 75 hours in that time, so I just use ordinary Shell Rotella T. If I were doing more than 100 hours in a year, but less than 200, I would switch to synthetic, and keep the yearly interval.

That's what I would do. YMMV.

BTW, I think the determination for diesel oil change intervals is mainly contamination. A diesel puts a lot of dirt into the oil, and the oil has a limited capacity to suspend it. Just try wiping the dipstick on a tissue, and you'll see what I mean. That's why I want to change the oil at least yearly, to flush out the suspended fine particulates.

Engines that have had regular oil changes look better inside. Clean surfaces in the heads, vs. dark or black deposits.

[Cheechako]

When cruising I usually did 100-150 hours depending on convenience and available oil supply.
I had a friend who had a 64 Chevy Impala (back in the early 70's) He never changed oil. Kept it for quite a while and still running when he bought another car. I just cant do that but a case for doing so could likely be made based on economics alone.

[Mike OReilly]

We have very different engines and different cruising grounds Ken, and I know very little about all this black magic, so far be it from me to give you any advice. I can say that I change mine at the end of every season, or when we hit around 100 hrs. But mine is an older Perkins 4108 (40 hp).

I’ve always appreciated the adage that oil is cheap, engines aren’t. Seems like cheap insurance to change the oil every 100 hrs or at the end of the season.

P.S. 100 hp! Holy schmolly. Can you get your boat up on a plane with that engine? I bet you could water ski. Me, jealous .

[drpaoletta]

The only way to really know is to use an oil analysis kit at intervals to see how quickly your engine degrades new oil. The analysis will also detect engine problems like coolant or water leaks that are too small to be visually detectable but will eventually cause serious problems. Google "Marine diesel oil analysis kit" - I found one with return postage included for less than $30. Every engine is different and the only smart way to extend service life of your oil is to have it analyzed by a lab.
- Personally I go by the manufacturers recommendation of 100 Hrs or annually.

[maxingout]

I change my oil every 100 hours on my Yanmar 3GM 30F engines. I also check the oil level before I start my engines.

[mcgann454]

Originally Posted by MarkSF

The manual for my Universal 5424 is now 33 years old. In that time, diesel fuel has gone from high sulphur to ultra-low sulphur, and engine oil from straight grade dino oil to multigrade with new options like synthetic, and semi-synthetic.

It's entirely appropriate to discuss this issue.

With a modern synthetic oil, I wouldn't worry too much about stretching out the engine hours a little, after all, most cars (including diesels) now run 10,000 mile intervals, which is equal to about 200 hours. However, they also require at least yearly changes.

My Universal gets oil changes every year, and it's done maybe 75 hours in that time, so I just use ordinary Shell Rotella T. If I were doing more than 100 hours in a year, but less than 200, I would switch to synthetic, and keep the yearly interval.

That's what I would do. YMMV.

BTW, I think the determination for diesel oil change intervals is mainly contamination. A diesel puts a lot of dirt into the oil, and the oil has a limited capacity to suspend it. Just try wiping the dipstick on a tissue, and you'll see what I mean. That's why I want to change the oil at least yearly, to flush out the suspended fine particulates.

Engines that have had regular oil changes look better inside. Clean surfaces in the heads, vs. dark or black deposits.

I am in the same boat so to speak as the OP. My research has also determined and I have been changing oil every year weather it needs it or not as the expense is minimal in my opinion. My question is related to timing. Would you do it at the beginning or end of the season? I have been at the end of the season to remove any moisture and I'm told oil can become acidic, but hate to have oil sit in the engine for six months. Short season in the great lakes.
Thanks in advance.

[S/V Alchemy]

Originally Posted by maxingout

I change my oil every 100 hours on my Yanmar 3GM 30F engines. I also check the oil level before I start my engines.

Same here...did it yesterday. I follow the manual on both the and use Rotella 15W40. It's cheap insurance. I do the same for my ZF25 hydraulic transmission: I follow the manual and the filter regimes.

I selected the shallow sump for my Beta 60 to reflect that I change oil pretty religiously.

[rwidman]

Originally Posted by Kenomac

Yeah, The service manuals recommend I have a Yanmar service tech do the work using official Yanmar oil. The engine is 16 years old, way outta warranty, so that isn't going to happen.

Yours truly has been the service tech for the past 7 years.

You don't have to cop an attitude about it!

If you are the "service tech" why are you asking random strangers on the Internet such basic questions as "when should I change my oil?"

[Kenomac]

Oops.... I'm mistaken, the Yanmar owners manual calls for oil changes ever 150 hours and gives a few oil recommendations. It was the Yanmar service center which recommended Yanmar oil and their service people. And it's seems the oil industry is the one that prefers my oil be changed one per year as indicated on the oil containers.

Westerbeke recommends 100 hours between oil changes.

What to do? I'm thinking 150 hours makes more sense for the Yanmar and 100 hours for the Westerbeke, along with some modern engine oil... I can't even locate any of the 16 year old stuff.

[Kenomac]

Originally Posted by Mike OReilly

We have very different engines and different cruising grounds Ken, and I know very little about all this black magic, so far be it from me to give you any advice. I can say that I change mine at the end of every season, or when we hit around 100 hrs. But mine is an older Perkins 4108 (40 hp).

I’ve always appreciated the adage that oil is cheap, engines aren’t. Seems like cheap insurance to change the oil every 100 hrs or at the end of the season.

P.S. 100 hp! Holy schmolly. Can you get your boat up on a plane with that engine? I bet you could water ski. Me, jealous .

If it'll make you feel better, we normally cruise along at 4-5 knots using only 30-40hp of the engine's capacity, or we motor sail using only around 20hp or so.