"Can use..." is not the same thing as a particular viscosity being the recommended or specified viscosity. There is only one car I know of that comes with 5w50 in the engine from the factory, and that grade is the sole recommended service fill.quote:
Originally posted by moribundman:
Well, my car's engine, per the manual, can use anything from 5W-20 to 20W-50/10W-60. My '89 listed 5W-20 to 20W-50. I suppose at temps under -10 C the asperities didn't exceed the physical thickness of the 5W-20.
Using Heavier Weight Oil
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EHD I think is more dependent upon oil type and
contact surface speed and load then a higher vis will be helpful but last on the list also EHD is more likly to form in a gear tooth or roller bearing EHD will NOT form in a plain bearing at all.
bruce
My conclusion after all of this is that in terms of engine wear or longevity, using heavier weight oils won't afford any real extra protection or advantage, but also that they won't hurt either. The only problem with them seems to be the decreased MPG, which is probably reason enough not to use them.
Apparently you haven't been reading the research papers. Bearing wear is the one area of least concern with lower viscosity oils.
Pontiac 326-455 CID from the 1970's.
Main bearings:
Clearance #1,2,3,4 0.0005" - 0.003"
#5 0.002" - 0.0035"
Connecting rod bearings:
Clearance 0.0009" - 0.0029"
1969 Blueprinted 302 SBC
Main bearings:
Clearance .002-.003 (.002 prefered)
Connecting rod bearings:
Clearance .002-.0025 (.002 preferred)
1975 SBC
Main bearings:
Clearance .0007-.003
Connecting rod bearings:
Clearance .0012-.003
1989 Toyota 7M-GTE
Main bearings:
Clearance .0012-.0019
Connecting rod bearings:
Clearance .0008-.0021
1989 Ford 3.0L V6 SHO
Main bearings:
Clearance .0011-.0012
Connecting rod bearings:
Clearance .0009-.0022
1996 Ford V8 SHO
Main bearings:
Clearance .0004-.0012
Connecting rod bearings:
Clearance .0009-.0023
2002 Honda V6
Main bearings:
Clearance .0008-.0017
Connecting rod bearings:
Clearance .0008-.0017
2003 Chevy LSx specs
Main bearings:
Clearance .0008-.0021
Connecting rod bearings:
Clearance .0009-.0025
What is equally important is the finish on the journals. The finish specification for most older cranks is typically 8 to 12 RA. But for newer engines that spec 5W-20/30 oil, the spec is 6 RA or less. GM calls for 5 RA on many of its newer engines.
You'll also find a similar trend in piston clearances, skirt coatings, and a change in metallurgy.
So...moving from a 10 cSt oil to a 14 cSt in a typical engine at operating conditions increases the minimum film thickness in the bearing how much? 1/2 micron? Wow-we-wow, that should surely allow the abrasive containments to pass right through your bearings a lot easier.
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427, I'm not worried about engine wear at normal operating temps. I'm interested in engine wear, or rather in preventing engine damage, in worst case scenarios -- which do happen.
Okay, so 20 weight oil used to be common (pre-1970s?), despite unrefined finishes and it didn't cause any problems (of that I'm aware). But according to AE Hase it's the smooth finish that makes the xW-20 oils work now!
I've used various grades of oils in my saabs and in my CR-V and never really noticed any decrease in mpg, certainly not a "substantial one." And that's w/ 4 cyl engines in all of them.
The recommendation in my 2001 9-5 manual is as follows:
SAE 5W-30 or 5W-40.
The oil should be semi- or fully- synthetic and fulfil the grade requirements for ACEA A3/B3 or API SJ. Oils which are less viscous, such as 0W/-40/50 are becoming more common and may be used. However, the oil must be fully-synthetic, of a well known brand, and fulfil ACEA grade requirements ACEA A3/B3 .
The recommendation in my 2001 9-5 manual is as follows:
SAE 5W-30 or 5W-40.
The oil should be semi- or fully- synthetic and fulfil the grade requirements for ACEA A3/B3 or API SJ. Oils which are less viscous, such as 0W/-40/50 are becoming more common and may be used. However, the oil must be fully-synthetic, of a well known brand, and fulfil ACEA grade requirements ACEA A3/B3 .
Come on moribundman, now you're just being silly.
I gave you the general case scenario. And if you talking the most severe, those extra cSt buy you even less MFT. Run through the bearing design equation yourself if you don't believe me. Look at the scientific papers that test ultra-thin oils. The effect on the bearings should be the least of your worries.
What AEHaas stated is correct. Only it just didn't happen yesterday, or some particular year, like 2001. Bearing tolerances and surface finishes have been steadily improving over the years as shown above. The difference between when 20 weights were used 40 or more years ago is that now they can be used under a greater span of temperatures and severity levels without any concern for lack of protection.
Now add the rollerized valvetrains, replacement of gear type oil pumps for eccentric types, distributor less ignitions, improved seal materials, improved metallurgy in pistons to control expansion, etc, etc.
So now when you see Honda or Ford or Chrysler recommend 5w20s for all temperatures, there are tangible reasons why they can do this safely.
So please, stop with this stuff about engines aren't different today then they we're 30 years ago. They are different. And the conditions for which the 5w20s are recommended for use are different.
I gave you the general case scenario. And if you talking the most severe, those extra cSt buy you even less MFT. Run through the bearing design equation yourself if you don't believe me. Look at the scientific papers that test ultra-thin oils. The effect on the bearings should be the least of your worries.
What AEHaas stated is correct. Only it just didn't happen yesterday, or some particular year, like 2001. Bearing tolerances and surface finishes have been steadily improving over the years as shown above. The difference between when 20 weights were used 40 or more years ago is that now they can be used under a greater span of temperatures and severity levels without any concern for lack of protection.
Now add the rollerized valvetrains, replacement of gear type oil pumps for eccentric types, distributor less ignitions, improved seal materials, improved metallurgy in pistons to control expansion, etc, etc.
So now when you see Honda or Ford or Chrysler recommend 5w20s for all temperatures, there are tangible reasons why they can do this safely.
So please, stop with this stuff about engines aren't different today then they we're 30 years ago. They are different. And the conditions for which the 5w20s are recommended for use are different.
427Z, I'm glad someone with your point of view and experience takes the time to post here!
I hope you don't tire of trying any time soon...love the chart you just put up. That's the kind of thing I have only guessed at, and never knew to be factual.
I hope you don't tire of trying any time soon...love the chart you just put up. That's the kind of thing I have only guessed at, and never knew to be factual.
"1sttruck, I'm guessing that you believe if you continue to repeat these same fallacies of relevance over, and over, and over again, you're going to get someone to believe you?
In the spirit of providing BITOG members with knowledge that is actually useful, let me suggest you produce some real factual evidence minus the logical fallacies to support your position. Or maybe you can't, because there isn't any?"
Some inferences drawn from facts may be subtle, but there is nothing hard here. It is however impossible however to do so when blinded by what appears to be some sort of cult induced dogma, which seems to be the affliction of some 5w20 advocates.
Looking at some studies which seem to do a decent job of distinguishing between friction and wear vs viscosity, one finds that like the rest of the world knows, everything else being equal a higher viscosity tends to produce a thicker oil film, which results in lower wear. In some cases a thinner oil can flow better and produce a thicker film at some wear points, but thicker oils produce lower wear overall. Differences are less with well designed bearings at operating speed, more apparent at dead center of piston strokes, and in some valve trains. Gears favor heavier oils, and one can assume that chains do too.
http://www.iantaylor.org.uk/papers/friction.pdf
The Piston Ring Contact (cont.) - Highest loads occur close to dead centre positions, and although speeds are low, "dwell times" are high. (chart shows higher wear for lower viscosity).
Valve Train Lubrication - Frequently the most difficult engine component to lubricate: thin oil films, high loads.
http://www.iantaylor.org.uk/papers/piston2005.pdf
Oil film thickness measurements - in general higher viscosity oils give thicker films. However, top ring film thickness could be thicker for lower viscosity oils.
http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?2005/TM-2005-213956.html
ABSTRACT:
The influence of lubricant viscosity and additives on the average wear rate of spur gear pairs was investigated experimentally. The gear specimens of a comprehensive gear durability test program that made use of seven lubricants covering a range of viscosities were examined to measure gear tooth wear. The measured wear was related to the as-manufactured surface roughness, the elastohydrodynamic film thickness, and the experimentally determined contact fatigue lives of the same specimens. In general, the wear rate was found to be inversely proportional to the viscosity of the lubricant and to the lambda ratio (also sometimes called the specific film thickness). The data also show an exponential trend between the average wear rates and the surface fatigue lives. Lubricants with similar viscosities but differing additives and compositions had somewhat differing gear surface fatigue lives and wear rates.
In the spirit of providing BITOG members with knowledge that is actually useful, let me suggest you produce some real factual evidence minus the logical fallacies to support your position. Or maybe you can't, because there isn't any?"
Some inferences drawn from facts may be subtle, but there is nothing hard here. It is however impossible however to do so when blinded by what appears to be some sort of cult induced dogma, which seems to be the affliction of some 5w20 advocates.
Looking at some studies which seem to do a decent job of distinguishing between friction and wear vs viscosity, one finds that like the rest of the world knows, everything else being equal a higher viscosity tends to produce a thicker oil film, which results in lower wear. In some cases a thinner oil can flow better and produce a thicker film at some wear points, but thicker oils produce lower wear overall. Differences are less with well designed bearings at operating speed, more apparent at dead center of piston strokes, and in some valve trains. Gears favor heavier oils, and one can assume that chains do too.
http://www.iantaylor.org.uk/papers/friction.pdf
The Piston Ring Contact (cont.) - Highest loads occur close to dead centre positions, and although speeds are low, "dwell times" are high. (chart shows higher wear for lower viscosity).
Valve Train Lubrication - Frequently the most difficult engine component to lubricate: thin oil films, high loads.
http://www.iantaylor.org.uk/papers/piston2005.pdf
Oil film thickness measurements - in general higher viscosity oils give thicker films. However, top ring film thickness could be thicker for lower viscosity oils.
http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?2005/TM-2005-213956.html
ABSTRACT:
The influence of lubricant viscosity and additives on the average wear rate of spur gear pairs was investigated experimentally. The gear specimens of a comprehensive gear durability test program that made use of seven lubricants covering a range of viscosities were examined to measure gear tooth wear. The measured wear was related to the as-manufactured surface roughness, the elastohydrodynamic film thickness, and the experimentally determined contact fatigue lives of the same specimens. In general, the wear rate was found to be inversely proportional to the viscosity of the lubricant and to the lambda ratio (also sometimes called the specific film thickness). The data also show an exponential trend between the average wear rates and the surface fatigue lives. Lubricants with similar viscosities but differing additives and compositions had somewhat differing gear surface fatigue lives and wear rates.
"Effect of Break-In and Operating Conditions on Piston Ring and Cylinder Bore Wear in SI (Spark-Ignition) Engines, Schneider et al:
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up)."
At start up the boundry and mixed conditions will obviously be prevalent, where a thicker oil film will help. Corrosion aside, piston engined private aircraft seem to favor single grade over multigrade oils, some believe in part because the films are thicker after sitting for long periods.
During warm up engine design and ambient temps will determine what weight of oil is best suited for minimum wear.
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up)."
At start up the boundry and mixed conditions will obviously be prevalent, where a thicker oil film will help. Corrosion aside, piston engined private aircraft seem to favor single grade over multigrade oils, some believe in part because the films are thicker after sitting for long periods.
During warm up engine design and ambient temps will determine what weight of oil is best suited for minimum wear.
"...some believe in part because the films are thicker after sitting for long periods."
Some think that engine wear during the first 20 minutes after start up is due to oil falling off the engine parts when at rest. I have never seen this in any scientific studies or in any SAE papers. I do not think this is relevant at all.
Many of the "thick is best" oil users quote this principal but it has never been written up. It is not mentioned in any chapter of the SAE automotive handbook or any oil related papers I remember reading within the last 10 years.
aehaas
Some think that engine wear during the first 20 minutes after start up is due to oil falling off the engine parts when at rest. I have never seen this in any scientific studies or in any SAE papers. I do not think this is relevant at all.
Many of the "thick is best" oil users quote this principal but it has never been written up. It is not mentioned in any chapter of the SAE automotive handbook or any oil related papers I remember reading within the last 10 years.
aehaas
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Sillyness is all that keeps me going.
"I'm a doctor, not an engineer."
- L.H.McCoy
I'm a sceptic. I'm also hard to convince that just because something works it is necessarily ideal.
I mentioned bearing clearances only because people keep saying they are smaller today and use that an as argument for why thinner oil works today.
Determining relevant information from inferences is apparently hard for YOU. Talk about a cult induced dogma, how about the PAB member fleet manager closed door meeting conspiracy? That turned out to be a big fat nothing.
That another favorite tactic of yours to bamboozle people. You only pick and choose studies, and information within studies to support your beliefs. You'd never survive critical peer review with such obvious prejudices like that.
Apparently you forgot to notice that the quote was a comment in regards to a simulation. Further the simulation was of a 10 Litre Diesel engine! But, given your track record to date, why am I not surprised.
Why am I not surprised you picked the Taylor paper with the instrumented diesel engine, instead of the one with the instrumented gasoline engine?
http://www.iantaylor.org.uk/papers/Additives2001.pdf
Could this be another example of the cult induced thick oil dogma selection process?
Hmmm. Let me play your little game now. I'll select from this study something that supports my position. "From figure 11, the lubricants B, D, and H have differing wear rates but similar viscosity values." Looking at the graph, we see that Lubricant H has about one third the wear of Lubricant B. Proving once again we can lower the viscosity without increasing the wear by just changing the formulation of the oil.
How's that grab ya'? Totally valid by the rules you play by.
Should we also mention that the oils in figure 11 have a viscosity from 4.3 to 9.0 cSt? That makes the thickest one no thicker than a SAE 20!!
OK, Bones. Just don't tell anyone I slept with a green skinned woman.
I am not sure why aviation and heavy truck articles are quoted as they have little overlap with cars. Also, the Shell aviation study stated that the Shell aviation oil was semi-synthetic and that the authors knew of no automotive oils that were semi-synthetic. This shows the age of the work done.
One article was published in 2000 so the work was in 1998-99 or so. Sorry but I see no relevance. And again, nothing to back up the claim of oil sitting on parts having any effect what-so -ever.
aehaas
One article was published in 2000 so the work was in 1998-99 or so. Sorry but I see no relevance. And again, nothing to back up the claim of oil sitting on parts having any effect what-so -ever.
aehaas
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Let's see, having an oil layer on sitting parts is not better than having essentially no oil on the sitting parts, but getting oil pumped as quickly to the dry spinning parts is of utmost importance.
Again, when I took the valve cover off and when I touched the cam lobes that had residual 0W-40 on them, the lobes felt essentially dry to the touch. The engine had been off for only a day. With a 5W-40, I got an oily finger. I believe it's better to have oil on sitting parts.
Here's another one of those famous leaps of logic.
From all these unconstrained variables:
From all these unconstrained variables:
The author of the article makes a conjecture:
Than subsequently dispells his own conjecture from the diesel engine study:
So instead of a scientific paper that AEHaas was referring to, we're left with moribundman's stinky finger.
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Would you please call it an empirical testing digit?
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