Originally Posted By: m37charlie
Originally Posted By: dnewton3
Originally Posted By: skyship
Important part I disagree with:
He may need a thinner lube; that would something that he can be the judge of, when it comes to starting ease. But it will NOT make any darn difference in wear.
I asked the senior geek in the ZF oil analysis lab out cold start wear, as I know him from visiting the R&D section every month and although they do mostly transmission fluid analysis, he did work for VW engine R&D before and is one of the leading bearing wear and oil analysis experts in Germany. His answer was based only on UOA results for VW diesels, so might not be applicable to truck engines.
The data file he quoted from was for a comparison of test rig data based UOA figures comparing a good quality 10/40 conventional with a full synthetic 0/40 doing multiple cold starts cycles with only 5 minute runs (The engine was in a freezer). The results were better with the 0/40 and when fed into a software program to figure out the TBO of a typical cars engine in central EU, it translated to a difference of just under 10%. BUT he would not comment on whether that was because one oil was synthetic and the other conventional or because one was an 0W. Both oils had the same Zinc and add pack contents, so it had to be one of the two factors. The only real conclusion I could get from him was based on his own old diesel van, as I asked him which oil he used and it was 15/40 in summer and 0/40 in winter.
Interesting, but not really easy for me to disect.
I do have some thoughts though:
1) whatever study this was, I really don't put much stock into it unless I can read it. I'm not saying you're wrong or being untruthful. I'm saying there is WAY too much left out to really understand the criteria of the German study. Plus, they often focus on models and lubes specific to their part of the world; perhaps not directly applicable to a Dmax in NA.
2) repeated cold starts with run times no more than 5 minuets? Several Q's here:
a) was the rig allowed to completely cool between starts?
b) was this a full engine, or just a sympathetic test rig?
c) what controls were in place?
d) what other characteristics were nullified as controllables?
e) the "results were better"? How defined? a 10% reduction in wear I presume? Over a period of what projected lifecycle? (IOW - if planned life is 400k miles, then would we expect 40k less miles of lifecycle? Should that matter to someone who only keeps a vehicle for 150k miles?) In essence, how does the projected lifecycle degredation compare/contrast to ROI?
f) Was there a manifestation of wear-rate shift tested at different OCI durations? (IOW - at what exposure duration was the test run at? Was it affected by OCI duration, if even tested at all as part of the DOE?) We know that nearly all lubes will be "better" when aged; so could the 10% difference be enhanced or diminished with shorter/longer OCIs? Many times these studies are run with "new" oils; that does NOT reflect a real world difference. As lubes age, the performance differential grealy shrinks; the perceived advantage of one lube over another reduces as they all beging to homogenize with OCI extensions.
g) does a 5 minute run time really reflect real world experiences for most of us? I understand that it might be significant to the study, but how many of us have this experience as the "normal" operational pattern for our engines?
Get the point? I'm not saying you're wrong, but I have a lot of questions about what the DOE was, how the test was set up and controlled, etc.
Here's my point to you, and to Charlie:
the real world application of these different lubes does not manifest into longevity issues in a Dmax.
I point to the data in my "normalcy" article. Consider the SAE paper (2007-01-4133) that shows lube wear rates drop all the way out to 15k miles. What that paper shows is that oil changed frequently has approximately a 33% higher wear rate towards the front of an OCI (certainly dependent upon lube and engine). Now, 33% sounds shocking, but you have to keep that in perspective. It is essentially the difference of wear rates dropping from 3ppm to 2ppm. And we MUST look at the exposure duration for those ppm counts to really understand wear rates. Folks - that just does NOT make any real difference in the lifecycle of an engine; at least not relative to the typical ownership lifecycle. As the OCI lingers on, the wear rates drop, pracitcally to zero in some manner. I point this out because there may be some German study that does show that a thinner lube makes a "10%" reduction in wear at uber-cold temps. But often those wear rates are so incredibly low already, that a 10% reduction means NOTHING in real world ownership criteria. The shift is basically moot; it's a fraction of an already miniscule wear rate. And what does one pay for that 10% gain in wear reduction? 2x+ more money, for a 10% reduction, resulting in a shift of total lifespan of equipment that the owner likely never hold onto long enough to realize?
The SAE study I reference shows that the tribochemical anti-wear layer is the number one thing that contributes to wear reduction, and that wear rates can be positively affected by running a longer OCIl. I agree that vis may or may not play a small part, but it simply pales in contrast to the other contributors, when the totality of wear is considered. Why is this? Because before pressure gets to float a part in a bearing, there is NOT much metal to meatl contact. It is essentially the two metal parts pressing their chemical-barriers together. As long as that anti-wear layer is intact, it retards wear until the pressure can float the parts on the hydrodynamic wedge. So, if a thicker lube does take a bit longer to get where it's going, you won't see wear escalate in the same magnitude relative to the time shift. IOW - it may take a thicker lube 3x longer to get to the upper end, but that 300% greater time may only make a 10% shift in wear. And that differential does not even show up in all engines; the Dmax seems nearly immune to wear. So that 10% German study may only reveal a 1-2% shift in a Dmax (I'm picking out ficticious numbers for an example here). Get the point?
I'm being specific to this engine family; it does not see much wear at all, and it really does not shift wear rates greatly based upon lube choice. A thinner lube here might well make the Dmax start a bit quicker, but it's not going to make the engine last much longer. The OP would have to run this rig out way past 500k miles to likely see any shift in the wear rates great enough to affect his ownership lifecycle. Is that REALLY going to happen?
I'm not saying you two wrong; I'm saying you haven't convinced me until I get to read, disect and understand the study you claim to support your position.
I agree that the OP is likely to benefit from a thinner fluid. But I stand by my statements that wear reduction isn't going to be one of them; not relative to the overall lifecycle of the Dmax engine, and the likely projected ownership duration. I've got about 600 UOAs of Dmax engines, running all kinds of lubes in all kinds of temps. I've seen the data much deeper and broader than most of you. My claims are backed up by my UOA macro data, SAE study, and the direct knowledge of this engine family.
I welcome your challenges, but please be specific and show how your data would usurp mine as it directly relates to a Duramax.
Is use of 50 wt oil a good idea in ANY engine a smart thing at -20F? If not then use of 15W40 is not a smart thing for cold soaked starts (except for block heater) at -40F. The viscosities are about the same.
You are smithing a lot of words, I think it verges on sophistry, in order to avoid the "embarrassment" of saying that someone who lives in a climate with significant exposure to -40C/F should use 0W30/40 or 5W30/40 in the winter - these are usually synthetics! Your anti synthetic bias has seemingly overwhelmed common sense; the OP asked a simple question that deserved simple answers. He can/should use CH4/CI4/CJ4 0 to 5W-30 or 40 in the Alberta winter.
Sorry for the rant.
Charlie
'
Thanks for the link and reference Charlie - I'll have to buy/review that SAE paper when I get back to work.
As for my point, I fully agree that the OP could benefit from a thinner fluid. I'm on record many times as saying that uber cold temps can be a reasonable condition to using synthetics, and this is one of those times.
But I'm trying to delineate the REASONS as why to use a syn here.
As for the ease of starting, etc. a syn makes sense here.
As for the wear differences, the Dmax simply does not show a lot of preference for lube grades, regardless of how cold it gets. Yes - I have several UOAs from super-cold saturated areas where normal fluids and syn fluids can be contrasted, and there is not much (if any) statistical shift in wear. That is presuming two things:
1) the engine comes up to temp at some point and is run a reasonable length of time (no short-cycle 5 minute runs in a lab freezer)
2) the engine is used in a reaonably normal manner
Probably 10% of my UOA data comes from cold areas (really cold from the upper plains). I fully agree that there is beneift to running a thinner fluid in those areas. But it's not wear-rates that are affected; it's ease of starting. And I would agree, when it's super cold, a syn can even make the difference between starting or even not staring.
But it really does not make a great deal of difference in wear rates.
How many UOAs do you all have for the Dmax? Do have have enough to run statistical delineation for grades, environments, etc?
Wear at start up is generally resisted by the anti-wear chemical layer moreso than the hydrodynamic wedge. At start up, engines are typicaly not under much if any load, and therefore the wedge is not nearly as important as when the engine is under load such as driving or pulling heavy loads. The wedge is very important to separate the moving/non-moving parts when loaded. But that wedge is not an absolute necessity when just turning at idle for several seconds. The anti-wear layer is what resists wear before pressure reaches all parts. And that is a function of the lube devloping and laying down the chemical barrier, and is dependent upon OCI.
I'll review the SAE paper you mention when I get a chance; thank you for the reference.
