I Am Tired of Hearing Oil Must Have a HTHS of 2.9 or 3.5 or Whatever

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For the first time I would ask for research articles that show these numbers are important. SL and SM 0/5W-20 oils have only been in common use for 4 or 5 years. Please refer me to an Original research article showing the use of fully formulated SL or SM API oils that shows wear rates and how a HTHS of 2.9 or 3.5 is needed. The only articles I have seen are 10 - 15 years old using non fully formulated oils. I want the original article, not an article that referrs to another article. aehaas
 
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I agree. Get the data out. What entertains me is when someone is choosing an oil, with all other factors are ignored, this person chooses an oil just because it has a HTHS of 3.1, vs an oil with say, 3.0.
 
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Making decisions based upon well-done science would seem to be a no-brainer. But, even when the science has progressed to a point that a consensus has been developed, there will still be those that find it is easier to make their decisions due to feelings...which are attitudes mostly born from old habits. From what I can glean in the few scientific morsels I've found, is it doesn't matter nearly as much as many people "feel" it matters in most passenger car applications. I hope your request turns up some good information.
 
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I'm ashamed to admit it, but I still have no clue what the HTHS numbers mean. I think that even if I took the time to study HTHS, my choices in oils would not be affected.
 
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As usual, I'm confused again. Specifically, can you clarify to what you refer when you ask "how HTHS..is needed". Are you asking for data that relates HTHS to wear as opposed to being related to lubricant thinning under specific conditions?
 
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This is a really balanced paper that was written it seems to demonstrate the safety of 5w20. Notice the testing is done with a 5w20 with an HTHS of 2.9(which BTW is the Minimum for an SAE 30wt so it's a HEAVY 20 wt being tested). They make a supposition ofan HTHS of 2.3 being safe but have no data supporting it. The best starts on Pg 20 web page [ February 12, 2006, 08:45 PM: Message edited by: Bryanccfshr ]
 
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AEHass, I do not have the article, nor the original references, but below is the abstract of a 1997 review of wear and viscosity. Note that the authors conclude a minimum HTHS cutoff of 2.6 to prevent wear. I recognize that the abstact is are review as opposed to an original work, but is this article in the general direction of your original question? copied from: http://www.tytlabs.co.jp/english/review/rev324epdf/e324ab_tohyama.html Technical Journal R&D Review Vol.32 No.4(1997.12) Research Report Low Friction Gasoline Engine Oil - Effects of Lower Viscosity and Friction Modifiers- Mamoru Tohyama, Toshihide Ohmori, Osamu Tsutsui, Masago Yamamoto Lowering the viscosity of engine oil is effective in reducing the fluid friction. However, it decreases the oil film thickness, and causes the increase in the wear of engine parts. Through the engine wear tests using an radioisotope tracer technique, it was clarified that an HTHS viscosity of 2.6 mPa¥s was the lower limit to prevent the increasing wear. It was also found that the influence of the lowering viscosity on the wear of piston rings was larger than that on the wear of the cams and connecting rod bearings. Addition of friction modifiers is effective in reducing the friction under boundary lubricating conditions. MoDTC was determined as an excellent friction modifier, after evaluating its effects on the friction of valve train and on the fuel consumption of engine. The effect of MoDTC on the friction reduction was considered to be caused by both of the MoS2 film formed and the rubbing surface smoothness that decreased the metal contact. From the results of these investigations, it was concluded that the points of designing low friction engine oil were lowering the HTHS viscosity to 2.6 mPa¥s and the addition of MoDTC. Based on this guideline, a low friction engine oil has been developed, and it contributes to the improving fuel consumption of automobiles.
 
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The SAE has literally hundreds of papers written on the effects of oil viscosity and bearing design. It's all there at SAE.org under publications.
 
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Bryan, nice article. Had to skip to pages 7-8-9 because of my lack of mathematical skill level, but those last pages, and last sentence, sums it up nicely.
 
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Thanks Titan. I prefer the safety factor of greater film thickness. It is interesting to note that the HTHS of the 5w20 in that model is 2.9 not the lower HTHS we are used to seeing in the majority of off the shelf 5w20's but rather the minimum HTHS requirement for SAE 30wt oil. It in theory is of little differnce to the 0w30 M1 I drained last month with an HTHS of 2.99
 
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All the Mobil 1 oils I've used are noticeably thinner than other oils rated at the same viscosity. I'm not measuring the viscosity, just watching it pour into the oil fill hole, and watching it pour out of the oil drain plug when warm. I wonder why Mobil does this? (Remember, this is just my impression, I could be wrong about actual measured HTHS numbers, PLUS, I certainly haven't compared them to every other oil out there.) Anyway, Mobil 1 5-20 is doing very well in my Honda Odyssey...what a powerful engine in that vehicle...and we've gotten over 30 mpg on 3 occasions!
 

AEHaas

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"I do not have the article, nor the original references, but below is the abstract of a 1997 review of wear and viscosity. Note that the authors conclude a minimum HTHS cutoff of 2.6 to prevent wear. I recognize that the abstact is are review as opposed to an original work, but is this article in the general direction of your original question? copied from: http://www.tytlabs.co.jp/english/review/rev324epdf/e324ab_tohyama.html" This is exactly the type of article quoted today that has no value on current motor oils. This study performed 12 years ago was before the development of current 20 wt. oils and uses non-API certified oil formulations. NO conclusions can be made regarding oil and wear based on todays oils. No relevant HTHS data is found in this article using API certified SL or SM oils. If you read this article carefully you will also see that they mention that the oils they did use did not directly relate wear to the oil film thickness of thinner oils. Ergo, thinner oils, particularly when it comes to ring wear did not result in more wear. But remember that they used oils that are by todays standards incomparable. So again, please refer me to an Original research article showing the use of fully formulated SL or SM API oils that shows wear rates and how a HTHS of 2.9 or 3.5 is needed. aehaas Thanks for the effort of looking it up. I know it is not easy to find these things.
 
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How would film thickness matter, as long as the parts do not touch? Thicker film tolerates larger contaminates, that's one reason. Areas of the engine get hottter than sump temp, there is another place that +150c visc might be relavent.
 
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Here it is in plain Japanese. Read the English Abtract on Page 1 I will Qutte long hand since the PDF is encrypted(which threw a wrench in my translating the rest of it as well)
quote:
Lowering viscosity of engine oil is effective in reducing the fluid friction. However, it decreases the oil film thickness and causes the increase in the wear of engine parts.
 
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This is not directly related to the question but is an interesting illustration of the corelation between decreasing HTHS and increasing wear Read Pgs 93-108 Page 107 has a graph depicting measured wear as HTHS decreases.
 

JAG

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The engineers at BMW recommended that the E46 M3 should use a very thick oil to help alleviate the premature failures these engines were having. VW strongly recommends oils meeting specs that require a HTHS of >=3.5 in many, but not all, of their engines. Some automakers in recent years recommend 5W-20 for normal use and 5W-30 for towing/extreme use. The lists could go on and on. My point is that these people have done the research, which we are not entitled to see. Articles would be interesting but unless they test many types of engines in various scenarios (torque, rpm, time duration, oil/coolant temperature, etc), the results will be a "data point", and not the full answer that you seek here. Each engine and usage condition combination is different. 5w-20 can be FANTASTIC CHOICE and same 5W-20 can be a STUPID CHOICE, depending on the application. Oil consumption should not be ignored as an important factor in suitability of an oil.
 
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