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One of None
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8,045 Posts
Discussion Starter #1
what is the really the right kind of oil for diesel engines?
15 w 40?
20 w 50
plain SAE 50 or 40?

What prompts me to ask this is yesterday's oil change project on my universal 5416. I waited for a nice cool overcast day... no sooner got the project started.. the sun came out! temp shot up to a close 90, in the boat easily 110! ARRRG! But, I stuck with and got it done. The jug of rotella I've been saving for this event is/was 15W40. Everything seems OK, oil pressure, sound, etc. I've always thought 20 w 50 was a better choice.
Please let me know if I'm not ok. WAIT! don't answer that! :D err.. I mean the oil :rolleyes:
 

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217 Posts
Hi there,
My perkins 4-236 owner manual asks for SAE 40 (Delo is one brand that I have heard is good to use). This seems to be a standard oil. Going to a standard automotive supply the 10-40w is way more common and won't wreck the motor immediately if that is all you can find.

Other engines have different requirements.

from your owners manual:
Use SAE 30 HD (CD) or 10W40 heavy duty diesel lubricating oil
http://monmouth.seasmember.com/KeelboatOday/Universal_Manual_2.pdf
 

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the pointy end is the bow
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6,265 Posts
Diesel motors require an oil that can withstand the soot and other particulates that end up in the motor oil. As far as whether to use multi-grade or a straight grade motor oil, I was of the opinion that straight weight motor oil was the best. I have since changed my opinion on that. Back in the 80's, I rebuilt motors in highway trucks. Cummins and Detroits were our bread and butter. Cummins was specific about using a multigrade oil in their motors. We had a customer come in after one of our rebuilds complaining about his oil consumption. He was using 30 wt oil instead of 10-40. We switched him over to the Cummins recommended 10-40 (or whatever it was) and the owners oil consumption went back down to normal. I was impressed. There is a difference and there is a reason why engine manufactures recommend certain oils.

Oh, and Delo-400 is one of the quality oils for diesel motors.
 

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Grasshopper
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908 Posts
I've been using Delo 100 40W in our older Pathfinder. Our manual says to change the oil and filter every 100 engine ours, but on a sailboat that could take a long time in getting a 100 hours on an engine. Acids build up when oil sits in a diesel for to long (not good for the engine), so I change out the oil and filter every 3 months wheather I hit 100 hours or not.
 

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Chesapeake Sailor
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579 Posts
Denise,

As you may know, the numbers refer to viscosity, "thickness" of the fluid. Multi range oils have become the de facto standard. A 15-30 oil supposedly has the ability to hold its viscosity through a range of temperature.

If you use your boat summer only, as most of us do. And you live on the hot steamy side of the continent, an SAE 40 would not be a bad choice. Though if you encounter a 30-degree F. day in August, the viscosity of your engine oil will make it tougher for your starter motor to turn the engine over.

Once started, the higher viscosity oil carries off heat more efficiently than the thinner oil. Any of the weights you listed will work. You will find that oil is like anchors in so much as everyone has a (usually emotional) strong opinion, seldom backed by anything more than anecdote.

Wayne
 

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ASA and PSIA Instructor
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4,163 Posts
Your engine manual should specify an oil type and weight, and the standards required of the oil. Diesels take a special HD formulation, the container should specify for diesel use. Heres what Westerbeke says:
"Use a well-known brand and try to use the same brand each time you change the oil. Avoid mixing brands of oil. Different manufacturers use different additives, and mixing brands may cause a problem if additives are not compatible. More important is to use the correct A.P.I. (American Petroleum Institute) and S.A.E. (Society of Automotive Engineers) ratings. For Westerbeke and Universal DIESEL models use A.P.I. code CF or CG-4, S.A.E. #30, 15W-40, 10W-30 or 5W-40."
 

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the pointy end is the bow
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6,265 Posts
Changing oil often is cheap insurance. According to the Chevron website, Delo-100 was formulated for 2 cycle diesels (Detroit Diesels)

Chevron Delo 100 Engine Oil
Chevron Delo 100 high-performance engine oils meet API service classifications CF-2 and CD-II (SAE 30, 40, 50) and CF and CD (all grades). These oils are designed to provide highly effective wear and deposits control in two-stroke diesel engines.
Delo: U.S., Canada & Mexico
 

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Somewhat Senior Member
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619 Posts
My boat gets only Shell Rotella 15-40. That's what the PO used for 10-years and he was on the Shell team that developed Rotella...if he believes in it, I believe in it. I'd be a fool to change.

MGM
 

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"'Hit don't make no diff'erns"

Those are the words of a diesel mechanic I work with. And when pressed, I have to admit, he made some sense.

Modern diesels run about 500,000 miles between rebuilds. That's about 10,000 hours.
So if you motor at 5 knots you'd have to drive your boat around the world twice in order to create enough wear to create a rebuild situation.

Just follow manufacturer recommendations and change about twice a year - even if you haven't used the engine. That's because oil is hygroscopic and absorbs water over time.
And be sure you are using an oil intended for diesels - it'll have a "C" designation (for compression ignition) instead of an "S" (For spark ignition) like gasoline engine oil.
 

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One of None
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Discussion Starter #10
thank the sea gods at least my diesel is ok... can't say dat bout me!
 

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You need to use "C" rated oil in diesels. The first letter in the API rating needs to be C. The weight depends on the temperature. Unless you use your boat in the winter a single weight oil is fine. My Yanmar calls for 30 weight for the temps. I operate in.
 

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The Universal manual calls for 10W40 or 30. Just make use you use an oil rated for use in diesels.
 

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██▓▓▒▒░&
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Denise, the "SAE" ratings are only relevant to one thing: How quickly does that oil flow through an SAE funnel at a specified temperature? Literally. That's all they measure, one temperature cold, one temperature hot, which is why some of them have a "W"inter rating as well as the single hot rating.

SAE ratings don't mean much.

The API "C" ratings for diesels ("C"ompression engines), and the "S" ("S"park)ratings are more important. A grade CD oil meets later specifications than a "CC" rated oil, and is obsoleted by a "CE" rating, etc. Same thing for the "S" series, the later in the alphabet that the second letter is, the newer the specs are. Sometimes that's not very relevant, but usually the later letter is the better product.

All oils with the same ratings aren't the same, but it is hard to find meaningful ways to compare besides reputation or brand name. Synthetic oils generally are built to higher standards, with added ingredients for better lubrication like molybdium sulfide dust, and the ability to provide "thin film lubrication" which protects your engine bearings during starting. The SAE specs don't rate those qualities at all.

So...any brand name you have faith in, that meets or exceeds the specs for your engine and the operating temperature range you will be running it in. If you want some fun, spend $25 on sending out an oil sample for testing once a year. The tests will show you if there is fuel or water or dirt contamination in the oil, along with trace metals that can warn you of bearing failures, etc. way before they are going to happen. Water contamination can come from simply not running the engine long enough and hot enough to cook off the normal condensation that forms in the oil, most of the sampling companies will tell you how to interpret their results.
 

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One of None
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Discussion Starter #14
thank you everyone! heading the Chessy in the morning! with luck I'll still be online with the wireless!
 

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Fascinating discussion, and one I'm very interested in right now. Especially MikeyMo's thoughts, since we own similar boats, but maybe not the same engines. I have just bought a Sabre 34-I (1979) with a Volvo MD11C, and the manual recommends 20W30. Can't find it anywhere (Pep Boys, Advance, WalMart, Sams, West). What do other users of Volvo's use?


Thanks,

Harry
1979 Sabre 34-I #063
Annapolis
 

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Harry, you have a 1979 boat with a 1979 engine operating manual?

Put it in perspective. In 1979 oils did not perform the way they do today, oil additives broke down way faster than they do today. If your manual calls for 20W30, think about what that means. Your engine needs 30 for normal operation, and Volvo is saying that's too thick for cold starting.

Today's 0W40 and 5W30 oils DID NOT EXIST IN 1979! But they would be fine for your engine (provided they are C-rated, not just S-) today. Volvo probbaly would have spec'd a 5W30, IF IT HAD EXISTED IN A QUALITY OIL PRODUCT BACK IN 1979.

If you do a web search on what the SAE and API numbers mean, the mystery goes away. Does a redhead or a blonde make a better spouse? (SAE numbers and hair color are both about equally relevant today.)
 

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HelloSailor, you hit on exactly my question. Yes, it's a 1979 engine. And, while I downloaded the manual this month, it's original to the vintage. And, yes, oil has come a LONG way in 30 years. I'm tempted to go with Rotella-T 15-40 (universally available high quality oil). The 40 is a touch thicker, but I doubt anyone will ever notice. And the startup at 15 would be nothing but good.

Harry
 

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Paul, I'm aware of the issue--or, the allegation that there might be an issue--but AFAIK the only problem is that a "slipperier" synthetic oil may get past aging parts faster than a thicker cheap dino crude. The W-weight shouldn't be much of an issue, as the engine heats up pretty quickly. If the engine is simply not leaking because it is so old and gunked up...Yeah, you've got a point. Then again, an old oilburner that blows smoke can run for a long time burning a quart every two weeks instead of getting a ring and valve job. that still doesn't mean it shouldn't GET one.

Don't slinkies push themselves down the stairs? (VBG)
 

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keep it clean!

:) Last I looked an atomic 4 was a gas engine:) but who cares? IMHO it is important to use C series oils in a diesel, Rotella being one of the better ones. 5 or 10 viscosity will leak thru a bad seal faster than 40, 40 will be harder to start, especially in cold weather. Within the same engine, temperature changes will determine the optimum viscosity, and as the engine ages and wears, a higher viscosity my become better because things don't fit as snug as they used to. Best place to start is from the owner's manual, but you will almost never hurt a diesel as long as you use a c series oil and change it regularly to keep it clean. Never go over 12 months on oil and filter, if you use it a lot change about 100 operating hours. Look at your dipstick daily, and don't panic if you just got your first diesel and see the oil is black! That's normal! Don't overfill, that is worse than running a pint low! Change it hot to get as much of that black gunk out as possible. An air leak or a clogged fuel filter will shut you down a lot sooner than oil. (I just spent the last two days cleaning a 30 year old diesel fuel tank):eek:
 
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