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Oil!

13K views 44 replies 21 participants last post by  T37SOLARE 
#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:
 
#27 ·
All i can say is ...WOW....
Ok, i am in this field and have worked with EG&G who are the people who build mutable engines and run them for very very long periods of time .. then dismantle them to figure out what works the best whether its fuel, oil etc..

15w-40 Rotella T is the only "presently on the market" oil that all of the major engine manufactures will warranty their engine under.. All of the Dello 30-40-50
will all be going bye bye soon because they can NOT be run in modern Diesel engines due to the amount of soot they produce. New Diesels 2009 and up will have to comply to the new EPA standard which means regenerative exhaust and egr systems.. " egr systems are now in use 2007 and up.
A re-gen is a muffler that has a cat built in it and self cleans... yes self cleans!!! to much soot 5k muffler goes bye bye..

Now, a Modern Direct injected Diesel turbo or not does require a good high detergent oil and a multi viscosity for millage and epa reasons.

A heavy weight oil is terrible on a diesel engine because its so thick it takes forever to reach every component during start up which is the most destructive time in the life of a diesel engine.. The longer it takes the more wear occurs! Also a heavy weight oil when cold will open oil filters by pass valves causing un filtered oil to be fed to an engine! Stop with the 50wt already...
An engine with heavy oil may kill its own oil pump the load is so great and most are gear pumps that the oil is large and sticky and puts lots of load on the pump which slow's down everything..

The concept is it is better to have thin coat of oil fast than a heavy oil much later..
A diesel engine at 200' on 15w-40 Rotella T almost stops wearing which is why " you may have noticed" all new Diesel run at much higher temps than they used to...
Now, i know i will get hate mail over this but this is what i do, i study,i live Diesel.. I have a Bachelors for A&M in M.E but i choose to work closely with Heavy Diesel whether its on land or in the sea. Yes i get dirty for a living and love every min of it.
 
#28 ·
It is always good to hear from an engineer, but how many of our diesel sailboat engines are such modern technology? Or could pass EPA requirements for vehicle use?

And then there are older engines, like the classic Mercedes diesels that wre intentionally built to consumer 1 liter of oil every 1000 miles in automobile use. Mercedes felt that it made more sense to consume oil than to put wear on rings--so they built engines that US customers would not accept. (I expect that's long changed by now, too.)

Different engineers, different solutions. So what do you recommend to the guy looking for staright SAE20 diesel oil today? Rotella 15w40???
 
#29 ·
Modern Mercedes are some of the cleanest engines on the road today " baring the old 300d converted to veggie or so.. Those waste as much as they burn lol.
Modern oil is so well refined its actually cleaner that the fuel we burn " which is sad'. I would move to Rotella T it is a damn good oil with the least side effects.. Now people with older 6v,8v 71's and so are going to be the ones to pay the price.. Those engine's if they have lots of wear can run away on the new thinner oils which makes it dangerous for them. I have even seen them run backwards!!! sucking in air through the exhaust and blowing out the air filter..

A word on the synthetics out there.
While there is little in the way of "good third party information that was not paid for" I do know of a company running Royal Purple 15-40 in a Nation wide fleet.
Here are the spec's.. One oil change per year! its a cool grand to do it in an on the road truck that gets 100-160k a year in millage! filter changes are the same and the wear is incredibly low. Now for the bad... an engine with rubber anything will leak!!! with no petroleum in the the seals shrink and crack as if dipped in gas. Most modern seals are neoprene or some form of synthetic which are not affected.

If and when you switch be prepared to change oil filters for a while. See rotella will clean out any thing in that engine and boat engines don't get many hours and cold run for way to long . So, in short it will begin to clean it all out and some will settle in the pan but most will be found in your filters.
 
#31 ·
So RichH, maybe you can answer my question. My new-to-me 1979 Volvo MD11C came with very specific oil recommendations by the engineers who designed it. I'm in your camp that the engineers are the experts (which is why I follow my Honda recommended oil change interval in my Honda, not the Jiffy Lube profit based 3K interval). They recommend 20W30 for my engine. After a couple of weeks of looking, I gave up and put in Rotella 15W40.

What would you use (include brand name and vendor) in an engine where the engineers recommend 20W30?

Harry
 
#32 ·
The suffix portion of the engine oil designation is the important one - the "30" for the 20W**30**. The suffix number is the required viscosity designation when the engine is at full designed operating temperature, not just the 'oil/water' temperature but the WHOLE engine. When the engine is at full operating temperature the clearances will be at the precise as designed distances, and the oil (at proper viscosity/pressure) will be properly 'supporting' those clearances, etc. The Prefix number is the apparent viscosity of the oil at ambient (cold) temperatures. The prefix number (viscosity at ambient temp.) allows less 'starting torque/friction' during the start-up process, and since the clearances are less at ambient than at operating temps. you develop the pressure (in the bearings) needed to support the hydrodynamic bearings ... faster. Most engine wear probably occurs during the start-up phase, when the colder engine temperatures have thermally 'shrunken' many of the clearances; if you dont want the higher friction, possible increased surface, etc. wear on an expensive engine .... then install a "pressure pre-oiler" in which the oil pressure (causing the bearings to be fully supported by the oil) is electrically (or manually) gained before any rotation of the engine parts - done on all the time on very 'expensive' engines. If you dont pressure pre-oil then the simple 'rules of thumb' developed nearly 140 years ago still apply .... "dont apply full load on any IC engine until its up to normal operating temperature" (and all the clearances have opened to proper dimensions). Ive used pre-oilers since I was a pup ... and routinely get 'several/many hundred thousand miles' out of an automobile engine (engine 'bottom', not valves and 'accessories', etc.). Should one use a pre-oiler on a marine engine? .... probably not $$ worth it as the typical boater only 'starts' the engine several time a YEAR and once started the engine runs at 'constant speed' and constant temp. for a comparatively long time - 'steady state' operation is 'very good' for an engine.

To answer your question ..... The manufacturer specified 20W30. If your engine is not starting up from below freezing temperatures, then ANY oil with a viscosity rating at '30 suffix' will be OK .... 5W30, 10W30, 20W30, straight 30 wt. will be suitable (the best match-up would be 10W30, in your case). Again, simply dont run hell out of the engine at WOT until the engine 'totally warms up' !!!!!!!!!!!

Another FAQ ... my engine is old, should I use a heavier oil ... the oil pressure is lower than when new? Probably not! Have a (very knowledgeable) mechanic check and possibly reset the oil back pressure valve so that the proper pressure (back to 'spec'.) is maintained in the journals ... if you cant maintain the oil pressure via pump adjustment (cant do this on many small engines), then its really time to 'rebuild the bottom' of (or replace) the engine as those designed clearances have 'opened up' due to adverse wear.

Moral: use the oil SAE grade 'as specified' (especially the 'suffix' number), dont run hell out of the engine until its fully warmed up.

Do I use synthetics? ... Yup, keeps the generated particles from combustion in suspension better, better handles the adverse 'chemistry' from the combustion (blow-by) process better, does deposit some 'chemicals' to the surface friction areas for better wear protection. BTW I use LARGE/oversized recirculation lube oil filters ... the largest surface area filter that will fit.
 
#33 · (Edited)
"If the original engine designer was clever enough to realize that the film strength of a certain viscosity oil "
Good answer 40 year ago but, like Bohr's Atom, a bit behind the times. As it was explained to me, by an engineering dean who made his income from a long list of combustion-related patents (he gets paid a bit every time a diesel-electric locomotive is built, among other things), what counts is not simply viscosity nor "film" lubrication. But, rather there is thick-film lubricaiton, and thin-film lubrication. And in the case of journal bearings, thick-film lubrication only counts when there is still oil flooding the bearings, i.e. during a hot restart. Once the oil has drained--and it must drain unless you keep the bearings immersed and foam the oil during regular operation--all that is left is a VERY THIN FILM of oil. At that point "thin film lubrication" is what counts, not viscosity.
There are oils, mainly synthetic oils with expensive additives, that literally harden up and turn into a sheet of glass when they are "struck" with a heavy load in the thin-film scenario. With these oils, or with this type of property, when your bearings start to slam around (and they always literally slam around during startup, before there is a thick film) they slam into a thin film of oil, which promptly acts like a sheet of glass, lubricating and protecting far better than any conventional oil could.

SAE ratings? all well and good, but I'm reminded of the Army commercail that showed a Bubba announcing "Ahs could hardly change the earl in mah car, but now the Army dun taught me to maintayn this heayh Apache helicopter!" (Yeah, well, remind me never to stand under one he's worked on while it is aloft. <G>)

Even the SAE's own web site will tell you that the oil rating (i.e. SD, SF, SM) says things that can be more important that the viscosity number. Viscosity counts--but no more than any one card in a winning poker hand.

"dont run hell out of the engine until its fully warmed up. " And for that we can thank sailors, in particular the United States Navy. Until they wrote a procurement specification for cars/trucks back in the 1940's, there was no standard for warm-up times. Then someone decided it would be nice if the targets could get moved around a bit more quickly when under attack. IIRC the original spec called for full and operational oil pressure within 20 seconds of start-up. Debates over heat loads, head gaskets, and other reasons to wait ten minutes can begin after that.
 
#34 ·
Hello - I think your hyperbole is showing tad too much. As one who actually designed/engineered such bearings, etc. and with a quite stong engineering tribology knowledge to boot, I'll stand by my statements. Thin film lubrication is of course important, but in the case of marine engines where comparative absolute time to need to protect the static friction phase of startup ... is minimal as a total. More marine, etc. engines have been ruined because of incompatible/inappropriate VISCOSITY oil, than ......... 'additives'. I'll stake my engineer/scientist's reputation on that one.
 
#35 ·
Well, Rich, it all comes back to the question of what can you do when the oil the manufacturer recommends may not be available, or not conveniently available.

He can buy 0W20 or 0W30, but 20W30 may be like hens teeth. You don't have to believe that 0W30 is better than 20W30 in every way. Maybe in a 40-year old dino oil it isn't.

But in a highly engineered synthetic? OK, tell the guy to mail order his 20W30 from an industrial supplier in Irkutsk, if that's the only place to find it. The point of the question was, originally, WHAT DOES HE DO WHEN HE CAN'T FIND THE OEM SPEC OIL?

"Find it anyway" would not be a useful answer to most of us.
 
#36 ·
I gave the best answer I could based on many years of actual technical/scientific/engineering experience: Use oil that has the 'suffix' number as specified and the closest (& next lower) prefix number .... whats the point of discussion of you fail to have any appreciation/comprehension/acknowledgement of that. The oil viscosity is dependent on temperature and if the operating temperature of the engine is at spec. for the 'suffix' number of the SAE oil rating then the engine will perform AT spec. This is not politics where the strongest and most developed 'presentation' and loudest voice 'wins'; this is just plain, simple FACT that is and has been accepted for the past 140 years. Unless you can intellectually present some supported and well document hydrodynamic 'anomaly', etc. to the contrary ... I simply dont intend to continue any further discourse on the matter. ;-)
 
#37 ·
Rich,

My question remains, and politics and engineering (I happen to be a Mechanical Engineer by degree, but oils are NOT my specialty) aside, reality comes into play. I understand the first number can run as low as possible, but where does one buy a 30 weight diesel oil? Rotella, arguably the best (or certainly a solid player in the game -- I don't want to start THAT argument!) only sells one multi-weight, and that is 15-40. In synthetic, I can get 5-40, but it's still 40. They sell single weight 30, but in a sailboat where a significant number of engine cycles are under 10 minutes (yet another problem, but is it better to shut it down cold, idle it until warm, or drive in circles to warm it up under load so you can shut it down?), the first number is fairly important. Ah, life is full of compromises. And as an engineer, I want "the single, only, provable right answer!"

Harry
 
#38 ·
This is a great discussion. I use synthetics exclusively in all my vehicles and boat. The only two 'readily' or 'regularly' locally available synthetics are the Rotella 5W-40 and the Mobil 1 5W-40 (Mobil is also the Delvac Synthethic, as I understand).

RichH or Hello, given these two choices, which is the preferred oil lube and why? Or, should the sailors who choose to use synthetics in marine applications try to source a different type online, etc. For this discussion, we can assume the manuf recommendation is SAE30, which I think is typical of most sailboat marine engines. It is in my Yanmar.

Jason
 
#39 ·
I just had to click on this when it got to 40 responses. It's oil, and you change it every 100 hours hopefully. Rotella 15-40 is approved by everyone, Delo (diesel engine lubricating oil) is also great oil. End of story. They will work in your engine.
 
#40 ·
JRD - thanks for bringing the discusssion back down a notch. I have the 28 year old Volvo whose instructions specify 20wt. No one, including Volvo sells 20wt. I have read and truly appreciate all the responses - adds to my knowledge - but I figure I'm doing harm by not deciding on something. I doubt I'll ever start the engine from below 32F but I do sail into the late fall and early spring. Since I have never changed the oil and don't know what is in it now, I want to decide on one and stay with it (I like to minimize mixing brands and types). I got some Delo 400LE 15W40 but will probably take it back and get some Rotella T 15w40. All the mechanics I had talked to said they would use straight 30wt. but from the sounds of things here, the 15 in the 15w40 should give me better protection when starting and warming up. That is my current plan - thank again to all.
harbin2
Islander 30, 1981
 
#41 ·
eh, me thinks winter is coming and us armchair sailors need lots of reading. Oil is oil but I know you guys really enjoy seeing it all slathered on the girls in the sun on the beach! Now I don't think the guys would mind talking about that kind of "oil" or would they???
 
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