"Synthetics have 700 times the shear strength"

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over conventional.I heard a popular on air tech go over these numbers again and again.Seems a bit off to me. He said by shear strength he meant the ability of the oil to stay inbetween metal moving parts over 700 times better then conventional oil causing much less friction.Could this be the reason for lower oil temps with synthetics also along with their ability to conduct heat better?
 
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I had an old petroleum engineer (a transplanted german by the way) tell me that the number is about 5 times. I would be more inclined to believe it is closer to that number.
 
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I dont know where these myths come from. Where is the test data to substantiate these claims? HTHS viscosity is the only industry-standard test for motor oil shear. HTHS numbers do not vary that much between different oils of the same viscosity, dino or synthetic.
 
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quote:
Originally posted by Jimbo: HTHS viscosity is the only industry-standard test for motor oil shear. HTHS numbers do not vary that much between different oils of the same viscosity, dino or synthetic.
I must agree with Jimbo. I can't understand how a synthetic could have seven-hundred times better shear strength than a comparable mineral lube...
 

MolaKule

Staff member
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Falex tests show the film strength of synthetics to be 7 to 9 times the film strength of mineral oils in units of psi. Basic film strength and "shear" strength are two different measures.
 

tpi

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So. CA
quote:
Originally posted by MolaKule: Falex tests show the film strength of synthetics to be 7 to 9 times the film strength of mineral oils in units of psi. Basic film strength and "shear" strength are two different measures.
Does this apply to group 3 synthetics also?
 
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Washington DC
quote:
MolaKule: Falex tests show the film strength of synthetics to be 7 to 9 times the film strength of mineral oils in units of psi. Basic film strength and "shear" strength are two different measures.
Right. The film strengths of polyalphaolefins, diesters, and polyolesters increase in the order that I just wrote them if I recall correctly. There are some SAE papers on increasing the film strength of Group IIIs and PAOs by adding diester or polyolester in small quantities.
 
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The title of this thread says "shear" strength, not film strength, as stated by 'cule. The Falex test is a low-speed high-load test. The lubricated parts in engines are subjected to high-speeds at low to moderate loads. Falex is not part of the API nor ACEA motor oil test sequences for good reasons. If synthetic fluids were really 700 percent superior in real-world engine conditions, conventional oils would already be specified out of existance by now.
 

MolaKule

Staff member
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True, But if film strength's can be improved (not duplicated) by addition of additives to mineral oils, then mineral oils would be the most economical. Film strength should offer advantages in low-speed startup and idling. The HTHS measure "theoretically" correlates better with in-service engine wear.
 

Alan

Thread starter
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This info came off Goss's Garage from Pat Goss,a local on air tech.He does seem extremly knowledgleable about cars and such,claims to be pretty knowledgeable in the field on lubrication as well. At first I thought he migh of said 7 times but nope he said 700 times.I've heard him state this on numerous occasions.Tune in if your in the DC Metro area. Once a guy correct him on the viscosity of gear lube as compared to PCMO and he seemed pretty annoyed by it. He was corrected by an email,maybe sent by one of you guys from Falls Church VA?
 
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quote:
Once a guy corrected him on the viscosity of gear lube as compared to PCMO and he seemed pretty annoyed by it.
lol ...at least here at BitOG, we can admit it if we don't know something.
 
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quote:
Originally posted by MolaKule: Falex tests show the film strength of synthetics to be 7 to 9 times the film strength of mineral oils in units of psi.
Perhaps the original quote was 700 percent, not 700 times. I would think this is PAO (7?) and esters (9?), and that Group III would vary from nearly 7 down to ?
 
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Maybe the shear stength was measured in stability, maybe the stability is "700" times greater, as in, it will "hold up" 700" times longer?? LOL, still a little off i guess. Just trying to make sense of this. What show or program spat out this info?
 
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quote:
Originally posted by Alan: This info came off Goss's Garage from Pat Goss,a local on air tech.He does seem extremly knowledgleable about cars and such,claims to be pretty knowledgeable in the field on lubrication as well. At first I thought he migh of said 7 times but nope he said 700 times.I've heard him state this on numerous occasions.
After watching Pat Goss a few times, don't you have to wonder if he really understands the difference between 700 times and 700%. If he actually said 700 times, that's prima facia evidence that he doesn't.
 
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I agree...I've only seen the 5X figure. But, why are synth's HT/HS's comparable then to dino of the same grade? In either case, I don't recall seeing any A3 rated dino oils....
 
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OK OK I don't know something. [Cheers!] I feel better already. ;)Sheer strength is it lost 2x faster in petroleum over synthetic.It is Sheer strength that is the most important of the 2 not film strength right. [Confused] [ August 31, 2004, 04:34 AM: Message edited by: dropitby ]
 
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