Diesel Engine Oil

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Maybe, but if you change the oil yearly, why not do it in the fall before laying up fir the winter?
 
djmarchand said:
When the Lehman manual was written, multi-grade oils had lower lubricating properties than straight grade oils, so they recommended straight. But today multi-grade oils have much better lubricity so I think you will get good performance witht he mult-grades. And in your climate you will get the benefits of easier starting when it is cold.
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This is right on the mark. Bob Smith and his 50-year-old manuals recommend straight grade oil. At the time of manufacture this was likely good advice. However, over the decades, as one might expect, there have been technological advances in the oil industry such that multi-viscosity oils are indeed better for even old, old engines. As far as the additive package being consumed, oil analysis will reveal that it does not come close to happening at the change intervals boaters employ. Your engine will be very much happier starting with multi-viscosity oils. Science, it's amazing, isn't it?
 
Bacchus said:
David

Thanks for the response. I'll apologize in advance for the lengthy reply but Ive seen many simple generalizations and the subject is far from simple.

I’m not surprised to hear you are an engineer based on your prior posts & valuable / common sense approach…
I’m a retired mechanical eng w/ no petro experience - just a curious type trying to learn more about diesels.

From what reading I’ve done my understanding is: (correct me if / where I’m off base w/ my assumptions)

Multi-Vis oils are comprised of 3 basic components

1) Base oil – I’m assuming it is multi-vis base oil is neither better nor worse than comparable single vis oil?

2) Viscosity Index modifiers –

a) Used to make a 10wt oil act like 30wt at higher temps to yield a 10W-30 multi vis oil
b) I can believe early VI modifiers were not as effective as modern ones (your point)
What I’m wondering is – are these newer ones actually better than the base oil and impact an improved lubricity that makes the multi-vis superior to single wt or is it that they now don’t detract from the base oil and they are equivalent?
c) I’ve read the following re: VI modifiers…
“Disadvantages
Unfortunately, viscosity index improvers do have some drawbacks. The primary disadvantage is they are susceptible to mechanical shearing. When referring to the slinky analogy, it is easy to imagine a stretched-out slinky cut in half by mechanical processes to produce two shorter slinkys.
As the additive is repeatedly sheared, it loses its ability to act as a more viscous fluid at higher temperatures. Higher molecular weight polymers make better thickeners but tend to have less resistance to mechanical shear. Lower molecular weight polymers are more shear-resistant, but do not improve viscosity as effectively at higher temperatures and, therefore, must be used in larger quantities.”
d) I am assuming the affect of c) above is that over time, as the oil ages & is stressed that the 10W-30 oil starts to act more like 10 wt oil at higher temps – not a good thing in our diesels!?
e) I’ve also read – “modern oils contain viscosity improvers, clever molecules that increase their length when hotter. These are designed to reduce consumption but do not improve the oil's lubrication properties.”
f) Based on e) above I draw the conclusion that regarding lubricity - modern multi-vis oils can be equal to single wt but not better?

3) Additive packages & API Ratings – this is where I get lost as to exactly what the various components of the additive pkg (AP) are and do. Again my reading leads me to believe the following:
a) Much / most of the difference in the latest / “improved” AP’s and latest API diesel ratings (CJ-4) have been pointed at / req’d to meet newer / lower emission regs in OTR trucks for diesels especially those w/ DPF’s (diesel particulate filters)… for example - I understand the level of detergents in CJ-4 oils is limited to reduce DPF plugging
b) One component of the AP is aimed at reducing the acids generated by combustion – this is the TBN # where higher has a greater capacity than lower #’s. I have seen a report that states “There is a great deal of evidence to show that use of an oil with a TBN that is too high for the duty can lead to several problems, particularly high wear rates of cylinder bores.”
c) My 2007 Yanmar 6LYA-STP manual recommends API CD 30wt above freezing (where I boat) or 15W-40 or 20W-40 where temps are below freezing. I’ve research newer manuals and see they have added API CF-4 & after the YM engine was introduced they included the CI-4 ratings but have not endorsed API CJ-4 oils – at least as far as I’ve seen.
d) One learning / conclusion is that the new CJ-4 oils MAY not be better than - in fact may not be as good as - the previous CF / CI-4+ category oils for us boaters (no catalytic converters or diesel particulate filters DPF's)

My take-aways and current practices based on all of this is:

1) Use a CF. CF-2 or CI-4 API rated oil – looking at Shell Rotella as an example that means straight 30wt which is CF/CF-2 rated (other brands e.g. Chevron Delo I consider equally suitable)
2) Avoid CJ-4 rated oils which again using Shell Rotella T Triple 15W-40 is rated CJ-4
3) I have no need to “cold start” my boat engine so see no benefit of multi-vis oil – other than it is readily available and reasonably priced due to the large volume used in trucks.

Most (not all) of the references above are from the Cox Eng Best Lubricants for Yacht Engines report I've referenced before & attached
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All this angst about additive packages and multi-viscosity oils is "much ado about nothing". Think just for a moment. There is not a single engine manufacturer in the world which does not specify the use of multi-viscosity oils and some of those recommend and use synthetics from the factory.
 
catalinajack said:
All this angst about additive packages and multi-viscosity oils is "much ado about nothing"..
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No angst intended. ..I'm just curiuos and trying to clarify & learn from a pro that worked a career in the industry.
I've used both and sleep well at night.
I do believe the Cox Eng report is science / fact based and I pay attention.
 
dhays said:
Maybe, but if you change the oil yearly, why not do it in the fall before laying up fir the winter?
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Agreed, but only if it truly needs changing due to its having reached its change interval. If not, leave it in and change it when it needs changing.
 
Bacchus said:
No angst intended. ..I'm just curiuos and trying to clarify & learn from a pro that worked a career in the industry.
I've used both and sleep well at night.
I do believe the Cox Eng report is science / fact based and I pay attention.
Click to expand...

The only pro that should be trusted when it comes to oil is a petroleum engineer. Boat mechanics can only pass on their anecdotal experiences which are, well, relatively limited and truly unscientific.
 
alormaria said:
This is a tough one.

My gut says to stick with what the engine is used to but my brain says to use the recommended straight 30wt.

The good thing is that it probably doesn't make any difference.
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:thumb::thumb:

In addition, when I first got to Maine, went to the store and discovered that ALL the fisherman use 15w/40 I started using that also. So the store had no straight weight oils.

Also in part because most people boat in warm, hot climates. I don't.
 
My oil analysis says if you are not going to run a specified oil...the oil analysis is a good idea to see what is happening with regards to the oil and engine wear.


Well my Lehman has about 2500 hours....mostly at relatively low RPMS (1700 on average)...half with 15W40 and half with 30Wt. All the engine oil analysis reports came back the same...basically no unusual wear or breakdown of oil or poor lubricity by the multi weight.


Use whatever you like...again...much ado about nothing.


Newer engines and the bet changes.
 
catalinajack said:
The only pro that should be trusted when it comes to oil is a petroleum engineer. Boat mechanics can only pass on their anecdotal experiences which are, well, relatively limited and truly unscientific.
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catalina,
I've been saying that for years!
And the information in manuals is largely gleaned from engineers. But more objective material is what engineers write in scientific data or even magazine articles. Auto mechanics not so much. In fact the most outrageous "old wives tales" frequently come from mechanics. It's unfortunate but common that mechanics put on the enngineers hat because they are asked to or because they are frequently looked up to as being very knowleable and it's hard to ignore sincere flatery.

My engine manual recomends SW and MV oils mainly because (IMO) most of the Mitsu S4L2 engines are used on generators or small tractors and back hoes. On a back hoe I'd use MV oil too but there's no reason to use it in most boat engines. If you don't need MV oil there's no good reason to use it.
 
"There is not a single engine manufacturer in the world which does not specify the use of multi-viscosity oils and some of those recommend and use synthetics from the factory."

True for TODAYS engines with computer assisted assembly.

Remember cars used to go under 100,000 miles till shot , today 300,000 is common with no special effort , just PM.

What oil is "best" for a 30-40 year old engine is what ever you can sleep at night with. Most boat motors are killed , not worn out.

Our 6-71 DD uses the 40 wt CF-II oil DD still recommends for their 2 stroke engines.
 
catalinajack said:
The only pro that should be trusted when it comes to oil is a petroleum engineer. Boat mechanics can only pass on their anecdotal experiences which are, well, relatively limited and truly unscientific.
Click to expand...

That is true. I only mentioned the Bob Smith experience because many folks blindly follow his advice.

I did also have a discussion with a engineer at Castrol some time ago regarding multi vs straight weight when I had my old Perkins T6.354.
His basic answer when I asked about using 20-50 was that I didn't need to spend that much money for the better quality oil. The straight would be "good enough" for my old diesel.
Yes 20-50 would be better but I didn't need it.
I went with 20-50 to attempt to stop all the leaks...it worked.:thumb:
 
What oil is "best" for a 30-40 year old engine is what ever you can sleep at night with. Most boat motors are killed , not worn out.

Our 6-71 DD uses the 40 wt CF-II oil DD still recommends for their 2 stroke engines.[/QUOTE]

I'm living this right now. I have 6-71s and SW 40 is becoming increasingly harder to locate.
 
mbevins said:
I'm living this right now. I have 6-71s and SW 40 is becoming increasingly harder to locate.
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Try a farm tractor dealership, if there's a cheaper option you'll find it there. My local guy has SW 40 by the gallon or 5 gallon bucket.
 
catalinajack said:
Agreed, but only if it truly needs changing due to its having reached its change interval. If not, leave it in and change it when it needs changing.
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Depends on how you define change interval. Cummins recommends 250 hours or 6 months for its QSB5.9 marine engines. Is that overkill? Maybe. On my sailboat I tried to change the oil and filters in the spring and fall (year round boating here remember). Not sure what I'll do with the new boat. It definitely will be at least once/year.
 
jleonard wrote,
"I went with 20-50 to attempt to stop all the leaks...it worked."

I started using Castrol 20W-50 on my older car that has a rear main seal leak causing clutch slippage. The PO used Risoline (very high detergent additive) for the previous 272,000 miles. The clutch slippage is very much reduced but I assumed it was because of the high detergent additive no longer being there.

I'm guessing your cessation of leakage was probably related to viscosity. But if it's something else I'd like to know what it is. I use Castrol in most everything except my boat. I started using Castrol in my motorcycle days.

dhays,
Spring and Fall is my basic change schedule also.
 
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I agree with the Rotella and regardless of wt ( climate conditions considered ) use Lucas oil additive this will prevent dry starts.
 
SD Pappy,
Rotella is definitely a high quality product as are other Shell products.
No such thing as a dry start though unless an engine sits for a year .. IMO.
 
There seems to be a little confusion about the W in some of the posts
The W stands for Winter, not weight.
A multigrade oil is measured at two different temperature points, one for Summer and one for Winter


They take a burette, a long glass tube with a petcock(valve) on the bottom and the valve has a certain hole size.


For winter the temperature is lower, 100 F, they open the valve and take the time it takes for a given amount of oil to flow through the valve


For summer, the temperature is higher, 212F,
Same thing, open the valve and take the time.


I have never seen a can of oil marked 30W, ie single Winter viscosity, on the can though in advertising I have seen the uninformed use this designation. So this would mean a single viscosity rated WINTER oil. 30W does not mean 30 weight


So a multigrade oil has additives that increase the viscosity through a larger range of temperatures. Which has been stated.
So if the oil has been enhanced and then measured at the 100F (Winter) burette, then it would be say 10W and also measured at the 212F (summer )burette, at say 30, then it
attracts the designation 10W30, read as 10Winter30


Newer diesel engines might spec a 15W40 oil and along with that a certain API (American Petroleum Institute) specifications. CJ-4, is one, and there are many for different applications. Then the engine manufacturer will state that their engines require a certain multi or single grade viscosity that meet their own specification.
Such as Volvo, VDS4, Volvo Drainage Specification 4, which I was at one time told that this means that the oil will adhere for a longer time before draining off the wear surface. I could not verify that this is what the drainage spec means.
 
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djmarchand said:
But some diesel manufacturer's either because they were stubborn, or know something that I don't know, never changed and still recommend straight grade oils. Cat and DD are two like that I know David
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David

You may want to double check this. My Cat oil charts show multi viscosity oils as commonly recommended. Not all engines mind you. My 3056s are recommended to use 15/40 wt.
 
sunchaser said:
David

You may want to double check this. My Cat oil charts show multi viscosity oils as commonly recommended. Not all engines mind you. My 3056s are recommended to use 15/40 wt.
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Cat 3116/3126 spec single grade. Apparently the high turbo boost with blowby mist cokes the oil and clogs the aftercooler. Similar situation on the Detroit two strokes, high temp at top ring cokes oil. Apparently the multivis oils break down at a lower temp.

Those are the only engines that I know of that spec single grade. Other Cats spec out 15-40.
 
It should be stated that 15-40W is 15 weight oil w an additive that gives it the viscosity of 40 weight at 212 degrees. The base stock is 15 weight oil.

In the early days of MV engine oil the VI was only effective for a short time so after 1000 miles 10-W30 was closer to 10 weight than 30. Do present day MV oil suffer to any degree from this viscosity breakdown?
 
Nomad Willy said:
It should be stated that 15-40W is 15 weight oil w an additive that gives it the viscosity of 40 weight at 212 degrees. The base stock is 15 weight oil.

In the early days of MV engine oil the VI was only effective for a short time so after 1000 miles 10-W30 was closer to 10 weight than 30. Do present day MV oil suffer to any degree from this viscosity breakdown?
Click to expand...

In several hundred oil sample analyses, I have seen no pattern of 15w-40 oil having viscosity out of spec at 100C. Unless there was fuel dilution. Otherwise, consistently in range.
 
Actually my oil analysis showed my 15W40 Rotella viscosity as "high" on most of my reports at both low and high temp ranges.....past spec numbers...but just barely and of no cause for concern by Blackstone.

No additives and anywhere between 100 to 200 hours on the engine.
 
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