The truth about 90w diff oil
02-23-2004, 04:31 PM
#1
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As many of you know, Honda specs 90w GL-5 or GL-6 for the differential. Period.
Let's dispense with the easy part first: There is no GL-6 API specification. It was proposed but never adopted. GL-5 supplanted GL-4, and since the extreme pressure (EP) carrying capacity of GL-5 is nearly twice that of GL-4, it is now nothing more than a historical reference in terms of high performance differential lubricants. GL-4 has applicability in some older transmissions, where the sulphur compounds needed for GL-5 are detrimental to yellow metals.
Now, here is where things are going to get interesting, and disturbing to some of you. Sorry, but the science does not lie.
The load capacity of 90w gear lubes varies, but it is generally higher than a 80w90 or 75w90 gear oil, even a synthetic oil. The load capacity is partly a function of viscosity, but more a function of the additive components. Nearly all gear lube manufacturers use sulfur and zinc compounds as their EP (extreme pressure) additives.
I have been analyzing Lubrication Engineers products, and in particular their 607 90w gear oil. First, because it is the only gear oil product they sell in quarts rather than 5 or 35 pounds buckets, 55 gal. drums, etc. In other words, it is useful for US.
Now, 607 is nothing special on the surface - it is a paraffinic base (mineral) gear lube, and contains the same EP additives as the rest. Amsoil 75w90 tested out at about 350 Newtons (N) in my EP testing. Better than most 75w90's. A very good product. But LE has one more additive up its sleeve, and it's a dandy.
LE 607 tested out at over 1000 N! This must be attributable to their Almasol EP additive, which is proprietary and made by their additive subsidiary. According to their specifications, it has higher load bearing capacity than even moly, on the order of 400,000+ psi. Huge. They also claim it is inert and attracted to metal, forming a coating which fills in the gaps between asperities in a manner which increases load carrying capacity, while reducing friction at the boundary level. We were able to verify this by using SEM analysis (scanning electron microscopy). We treated a gear system with the 607 and ran it at high RPM, then removed a section for analysis. The treated metal looked very smooth compared to the untreated metal. This reduces friction and should result in lower operating temperatures.
The 607 was extremely low in adulterants, indicating it is made of very highly refined base stocks. It has no VI additives, of course, since it is a single-grade oil. It will also have complete shear stability. It is purple in color. The TBN was 1.5, typical for a gear oil. The flash point was around 400degF, somewhat lower than usually seen in a 90w, but inconsequential.
It has a pour point of -11degF, below which it will be extremely thick. So it is not for Arctic use for sure, but then, no 90w is.
By comparison, the Amsoil has a pour point of about -46degF. By other comparison, Schaeffer's 90w bottoms out at 0degF.
LE also makes some synthetic 90w gear oils, made of PAO's and esters, but without the Almasol EP additive. The pour point is extended to about -27degF.
So, there it is. Honda's recommendation is clear, and we have found at least one product meeting the specification that is a cut above anything I have seen in this grade. It offers four times the load carrying protection of the 75w90's most of the people on this Forum have used as a replacement for the factory fill. Since most dealers are clueless and I have little hesitancy to say this, I would wager that the "service lube" at most dealerships will not even be 90w at all, but likely something like "good ol' Pennzoil 80w90" - the same stuff you would find at a corner service station, covered in dust, if corner service stations still existed.
The LE 607 is widely used in racing, and by many Nascar teams, according to my contacts in the industry. I cannot verify that, but based on its analysis, that would not be surprising. Its performance is quite amazing.
So, what inferences can we draw? Does Honda spec 90w for any of its other vehicles? If not, might it be for good reason? Does the S2000's ring/pinion need a high vis, high-performance gear for best reliability? Why has Honda been so "obtuse" in specifying a lubricant type that is not in their parts chain, not easily sourced by customers, and would require extensive lubricant knowledge by service technicians, assuming they were even to bother to try to source an "industrial lubricant" from a company like Lubrication Engineers, or one of the "Bigs"? Are at least some of the differential failures reported by "hard running" attributable to the reduced shock loading capabilities of non-spec lubricants (that is, non 90w)? Can the service life of S2000 diffs be materially extended by a hi-performance 90w, considering that "mere" 75w90's have been used successfully?
I realize I have posed many questions, but also provided a number of irrefutable facts here.
Considering all the facts known to me and my own use requiremnents (garaged car, not driven in extreme cold, driven hard in hot weather), I will be switching over to LE's 607 at about 1000 miles.
Let's dispense with the easy part first: There is no GL-6 API specification. It was proposed but never adopted. GL-5 supplanted GL-4, and since the extreme pressure (EP) carrying capacity of GL-5 is nearly twice that of GL-4, it is now nothing more than a historical reference in terms of high performance differential lubricants. GL-4 has applicability in some older transmissions, where the sulphur compounds needed for GL-5 are detrimental to yellow metals.
Now, here is where things are going to get interesting, and disturbing to some of you. Sorry, but the science does not lie.
The load capacity of 90w gear lubes varies, but it is generally higher than a 80w90 or 75w90 gear oil, even a synthetic oil. The load capacity is partly a function of viscosity, but more a function of the additive components. Nearly all gear lube manufacturers use sulfur and zinc compounds as their EP (extreme pressure) additives.
I have been analyzing Lubrication Engineers products, and in particular their 607 90w gear oil. First, because it is the only gear oil product they sell in quarts rather than 5 or 35 pounds buckets, 55 gal. drums, etc. In other words, it is useful for US.
Now, 607 is nothing special on the surface - it is a paraffinic base (mineral) gear lube, and contains the same EP additives as the rest. Amsoil 75w90 tested out at about 350 Newtons (N) in my EP testing. Better than most 75w90's. A very good product. But LE has one more additive up its sleeve, and it's a dandy.
LE 607 tested out at over 1000 N! This must be attributable to their Almasol EP additive, which is proprietary and made by their additive subsidiary. According to their specifications, it has higher load bearing capacity than even moly, on the order of 400,000+ psi. Huge. They also claim it is inert and attracted to metal, forming a coating which fills in the gaps between asperities in a manner which increases load carrying capacity, while reducing friction at the boundary level. We were able to verify this by using SEM analysis (scanning electron microscopy). We treated a gear system with the 607 and ran it at high RPM, then removed a section for analysis. The treated metal looked very smooth compared to the untreated metal. This reduces friction and should result in lower operating temperatures.
The 607 was extremely low in adulterants, indicating it is made of very highly refined base stocks. It has no VI additives, of course, since it is a single-grade oil. It will also have complete shear stability. It is purple in color. The TBN was 1.5, typical for a gear oil. The flash point was around 400degF, somewhat lower than usually seen in a 90w, but inconsequential.
It has a pour point of -11degF, below which it will be extremely thick. So it is not for Arctic use for sure, but then, no 90w is.
By comparison, the Amsoil has a pour point of about -46degF. By other comparison, Schaeffer's 90w bottoms out at 0degF.
LE also makes some synthetic 90w gear oils, made of PAO's and esters, but without the Almasol EP additive. The pour point is extended to about -27degF.
So, there it is. Honda's recommendation is clear, and we have found at least one product meeting the specification that is a cut above anything I have seen in this grade. It offers four times the load carrying protection of the 75w90's most of the people on this Forum have used as a replacement for the factory fill. Since most dealers are clueless and I have little hesitancy to say this, I would wager that the "service lube" at most dealerships will not even be 90w at all, but likely something like "good ol' Pennzoil 80w90" - the same stuff you would find at a corner service station, covered in dust, if corner service stations still existed.
The LE 607 is widely used in racing, and by many Nascar teams, according to my contacts in the industry. I cannot verify that, but based on its analysis, that would not be surprising. Its performance is quite amazing.
So, what inferences can we draw? Does Honda spec 90w for any of its other vehicles? If not, might it be for good reason? Does the S2000's ring/pinion need a high vis, high-performance gear for best reliability? Why has Honda been so "obtuse" in specifying a lubricant type that is not in their parts chain, not easily sourced by customers, and would require extensive lubricant knowledge by service technicians, assuming they were even to bother to try to source an "industrial lubricant" from a company like Lubrication Engineers, or one of the "Bigs"? Are at least some of the differential failures reported by "hard running" attributable to the reduced shock loading capabilities of non-spec lubricants (that is, non 90w)? Can the service life of S2000 diffs be materially extended by a hi-performance 90w, considering that "mere" 75w90's have been used successfully?
I realize I have posed many questions, but also provided a number of irrefutable facts here.
Considering all the facts known to me and my own use requiremnents (garaged car, not driven in extreme cold, driven hard in hot weather), I will be switching over to LE's 607 at about 1000 miles.
02-23-2004, 08:50 PM
#4
Great stuff, RR. 
I wonder if your lab has tested any of the Redline gear oils? Alternately, what do you make of their claims here: http://www.redlineoil.com/redlineoil/spgoti.htm
I've used the Shockproof Heavy with no apparent ill effects for several thousand track miles.
Cheers,
John
I wonder if your lab has tested any of the Redline gear oils? Alternately, what do you make of their claims here: http://www.redlineoil.com/redlineoil/spgoti.htmI've used the Shockproof Heavy with no apparent ill effects for several thousand track miles.
Cheers,
John
02-23-2004, 09:13 PM
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Originally posted by fly_S2K
RR where could one get a hold of this LE 607 90w gear oil?
RR where could one get a hold of this LE 607 90w gear oil?
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02-24-2004, 04:20 AM
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RR
What about the limited slip additive for regular dif lube? I added this to clutch-pac limited slips to reduce chatter in previous cars.
Does it have any benefit in our torsen type rears?
It is billed as a "friction modifier", how does it 'modify?
Thanks
Frank
What about the limited slip additive for regular dif lube? I added this to clutch-pac limited slips to reduce chatter in previous cars.
Does it have any benefit in our torsen type rears?
It is billed as a "friction modifier", how does it 'modify?
Thanks
Frank
02-24-2004, 06:07 AM
#10
RR, very interesting. Currently I'm using Redline 75w90.
FWIW, here's some notes I've made on the differential.
TSB 011001 Differential - GL6 gear oil not available for S2000 differential
Differential Fluid: Per Honda
FWIW, here's some notes I've made on the differential.
TSB 011001 Differential - GL6 gear oil not available for S2000 differential
Differential Fluid: Per Honda
