Yeah, that was it. So cool. I always valued his opinion (and Gary's) because they did real world analysis. Gary tested thin oils on his own Jeep and BGN tore down his own engines to determine what happened.
Will Thinner Oils Damage Your Engine?
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There would undoubtedly be a difference in the UOA on an engine with a sudden catastrophic failure in it and an engine slowly wearing. We just don´t know enough about those failures to know how much material wound up in the oil that was sampled. I don´t think it really adds much relevance to this discussion. But that´s just my humble opinion.
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It wasn't catastrophic in the sense that it tossed a rod. He had significant bearing wear, yet no evidence of that in his UOA's because the particles being shed were too large to be picked up by it. I'd call it reasonably rapid wear perhaps?
Ok but that 50s 5.2L V8 had like.....200hp (or even less)....
And cars of that era never made it to 100.000kms anyway (due to inferior metalurgy of that time)
Their engines got rebuilt before no matter what oil was in there
Back in the day when I ran UOA in college we would get samples with visible particles in the oil that would test "normal". Granted this was using atomic absorption with a relatively short residence time in the plasma rather than today's ICP. Back then we had to perform an acid digestion to get a better idea of how much metal was really in the sample. But in general a catastrophic failure where metal pieces came off did not show high wear metals.
This illustration is lifted from a Machinery Lubrication article, you can see that only relatively small particles are detectable via emission spectrography:
And by that description right there, regarding the size of particles, it is unrelated to this discussion and also does nothing to discredit UOAs as they relate to the discussion. Also, in my book, throwing a rod is a catastrophic failure. But again, opinions may vary. These are simply my own.
That's interesting. Maybe the previous UOAs were showing the issue or the trend and the final UOA (if the timing is right), may not reveal any additional info. is that right?
btw that's why I don't do uoa because I don't want another continuous task. lol if it was a one time deal, I would consider it.
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Ok, I didn't see the "particles too big to be detected" post . I must had been 1 page behind when I posted.
It might still be running if he ran 5W30 in it.@BlakeB nailed it. So the correction is: If it wasn´t for start-up wear, they´d make it the equivalent of around the moon and back, probably 3 times or more before wearing out.
To the original question, regarding the Pentastar tear-down after it finally failed after 625k miles: It ran primarily on Valvoline 5w20. I´m sure that it would have made it to 626k miles if he had run a thicker oil, so the answer is yes, thinner oil causes more wear.
It might still be running if he ran 5W30 in it.
Interesting point but the manufacturers aren't going to help here. They give a hang about two things passing the CAFE rules and regulations and selling new junk.
or W40It might still be running if he ran 5W30 in it.
OVERKILL
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I'm saying it DID NOT toss a rod, that's why I said it wasn't catastrophic failure. He had some rather significant bearing wear upon tear down, which was done because he had observed reduced oil pressure. This was after having a UOA done which showed nothing abnormal.
Filter probably caught a lot of the wear debris, and the particles that did make it through still might have been too big to get solid UOA info. Guess it shows that UOAs might not even show that an engine is eating itself, like in his case with significant bearing wear.
Yes.
Picked up that bad habit from edyvw
" xW-40 " gets the point across better. W40 ... could be WD40, lol.
With the toyota, it wasnt that it was lugging the engine - infact it doesnt have much power (inline 2.5) at lower RPM to lug it. The issue was the shift logic was very very rough at low speeds and would do erratic unexpected downshifting. Like say it was rolling in 3rd gear at 15-20mph and you wanted to get on it for a bit more power, it would downshift to first instead of second which is not what the driver would expect in that situation according to the physical gas peddle.
I'm not sure about thicker oil for lugging engines, what I know about HTHS is the shear is higher at higher rpm. So it might not make a difference. Lugging aint a good ideal anyway, and in that situation I would probably give more throttle to prompt a downshift.
Lots of people point to UOAs of 20 grades that do well, but you don't know the driving style of the person or transmission of that engine. For the sea of turbo crossovers you see on the streets with automatic transmissions, most keep the RPMs sufficiently low enough to get the required torque to move. Those people aren't ripping the throttle anyway.
I don't want to run a w40 which has a much higher SAE limit of 100 cST than the factory spec w20 just to get better HTHS - for my miata. In europe this car specs either 0w20/5w30 A3/A5. All I'm saying is it would be nicer if USA oil companies were more transparent about the specs like "euro" oil companies. Japanese OEMs dont use approvals besides API. The only approval I'm familiar with is Dexos, which doesn't say much about HTHS. Trying to navigate Euro OEMs approvals requires a dictionary.
Lower revs shouldn't hurt the shearing viscosity like a very high revving engine would, but lower revs does also decrease the MOFT which keeps parts separated, which is why a thinner oil won't give as much protection on a low revving/lugging engine compared to thicker oil - ie, the bearing's hydrodynamic wedge collapses with lower revs. As revs go up, the shearing viscosity (HTHS) decreases some which hurts MOFT, but MOFT also increases more with revs (ie, the bearing trys to self center and increases the wedge thickness). Most passenger car engines would have to rev quite high to get beyond the shear rate where standard HTSH is measured.
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And meeting their specific durability goal, which probably didn´t change when they changed oil weight for Cafe. They likely kept the same goal, which, for example, might be 150k miles. So the oil weight becomes a non-issue, from their perspective. If they thought the engine wouldn´t make their goal on the lighter oil, they´d make design changes to ensure that it would. That´s why FCA would put the coating on parts whose wear is affected by ESS in the Pentastar. They still have to meet their standard, whatever oil is in there.
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