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#3329892 - 04/01/14 02:08 AM How to match gear oil to application?
NMBurb02 Offline


Registered: 09/12/12
Posts: 1362
Loc: Crowntown, CA
I have decided to use a 75W-90 GL-5 synthetic gear oil for my upcoming front and rear diff fluid changes on the Burb, but there are quite a few choices out there. Aside from personal preferences and testimonials I have read on BITOG (most of which have been comments that such-and-such brand works fine in the poster's application), I have not come across anything that really explains how to compare fluids in the same grade to determine what might be the best choice in a certain application. I could go the route of doing multiple UOAs using different fluids, but the drain intervals for my application are 100k+ miles (in fact, the owner's manual includes fluid level checks every 7,500 miles, but never calls for fluid changes), so that does not seem to be a very effective way to go.

Is there a simple way to match a gear oil's performance specifications to an application to choose the best fluid? Gear oil PDSs do not contain much information, so can any reasonable conclusions be drawn by comparing viscosity and VI numbers for fluids in the same grade? Are 100C and 40C viscosity numbers even directly applicable to differential operations (I have no idea what normal differential temps are)? How much of a role does VI play?

For my particular application, the Burb is used primarily as a kid hauler, with the most frequent trips being 12 to 25 miles each way, mostly highway. It will also see road trips of 700+ miles once per year (with a 3,000 mile round trip that involves passing through the Rockies coming up in a few months). In the nearly two years we have owned the Burb, we have never used it to tow and I do not see doing so any time soon. I am located in Southern California, so this vehicle is not driven in low temperatures, and if it ever is, it will most likely be above 0F. So I am basically looking for a fluid that provides adequate protection under this light duty cycle and any possible MPG benefits from reduced friction during short to medium distance driving. In my quest to compare the available fluids, I put together the following table based on current PDSs, with fluids listed lightest to heaviest at 100C:

Code:
Fluid			100C, cST	 40C, cST	Viscosity Index

Mobil 1 LS		14.6		103		146
Castrol Syntrax		15		111		???
Valvoline SynPower	15.6		100		150
Peak GL-5		15.9		104.7		162
Redline GL-5		16.4		115		155
AMSOIL Long Life	16.6		129.7		137
AMSOIL Severe Gear	16.8		109		167
Royal Purple Max Gear	17.5		119		???


If lower viscosity equals better fuel efficiency (is that a valid assumption?), looking at it on paper, Mobil 1 appears to be in the lead when it comes to overall fuel efficiency due to it having the lightest viscosity at 100C and second to lightest viscosity at 40C, although it is among the lowest VI. If I was planning on moderat towing or occasional mid-high load, mid-high shock runs, I should lean toward RP or AMSOIL (as I understand it, if I was going heavy load/shock, I would bump up to 75W-140 or 85W-140), right?

So based on the information and assumptions above, product availability and price, and testimonials I have read on BITOG, I have decided to go with Mobil 1. Are there any flaws in my reasoning? I am looking for gear oil education as much as a specific product recommendation here.

[As an aside, I found Valvoline High Performance Gear Oil (conventional) to have interesting numbers of 15.47 cST @ 100C, 99.0 cST @ 40C, and a VI of 166, which, if compared to the fluids in the table above, would be the third lowest 100C number, lowest 40C number, and second highest (by 1 point) VI. Maybe it is a viable option with 25-50k drain intervals?]
_________________________
2002 Chevy Suburban 1500, G-Oil 5W-30, Napa Gold FIL 4805
2006 Pontiac Grand Prix GT, Valvoline ML NG 10W-30 +MMO, Puro PureOne PL10111

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#3329894 - 04/01/14 02:49 AM Re: How to match gear oil to application? [Re: NMBurb02]
Black_Thunder Offline


Registered: 09/23/06
Posts: 822
Loc: Wisconsin
out of the list shown I've only used the Mobil and Valvoline.

I've used other gear oils like conventional store brands like farm-rated or supertech etc.


either way I'd say any of those would work just fine i guess whatever you can find readily available.

probably wouldn't even have a problem running supertech synthetic.

I don't really think 140 is needed unless its spec'ed for it like some ford truck axles but they usually have limited slip.


All the class 8 semi trucks i work on run 75w90 in the axles and hubs, of course thats a lot more oil then a light truck axle but i think thats something to think about.
_________________________
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#3329900 - 04/01/14 03:24 AM Re: How to match gear oil to application? [Re: NMBurb02]
wirelessF Offline


Registered: 10/04/07
Posts: 1269
Loc: Oahu, Hawaii
Eneos 75W90 has the lowest cST @ 40C and highest VI from looking at your list.

Kinematic viscosity
(40°C), mm2/s 82.0
(100°C), mm2/s 14.7
Viscosity index 188
_________________________
For racing or off-road use only!

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#3329907 - 04/01/14 03:45 AM Re: How to match gear oil to application? [Re: NMBurb02]
Ducman Offline


Registered: 03/18/13
Posts: 233
Loc: Australia
Originally Posted By: NMBurb02
I have decided to use a 75W-90 GL-5 synthetic gear oil for my upcoming front and rear diff fluid changes on the Burb, but there are quite a few choices out there. Aside from personal preferences and testimonials I have read on BITOG (most of which have been comments that such-and-such brand works fine in the poster's application), I have not come across anything that really explains how to compare fluids in the same grade to determine what might be the best choice in a certain application. I could go the route of doing multiple UOAs using different fluids, but the drain intervals for my application are 100k+ miles (in fact, the owner's manual includes fluid level checks every 7,500 miles, but never calls for fluid changes), so that does not seem to be a very effective way to go.

Is there a simple way to match a gear oil's performance specifications to an application to choose the best fluid? Gear oil PDSs do not contain much information, so can any reasonable conclusions be drawn by comparing viscosity and VI numbers for fluids in the same grade? Are 100C and 40C viscosity numbers even directly applicable to differential operations (I have no idea what normal differential temps are)? How much of a role does VI play?

For my particular application, the Burb is used primarily as a kid hauler, with the most frequent trips being 12 to 25 miles each way, mostly highway. It will also see road trips of 700+ miles once per year (with a 3,000 mile round trip that involves passing through the Rockies coming up in a few months). In the nearly two years we have owned the Burb, we have never used it to tow and I do not see doing so any time soon. I am located in Southern California, so this vehicle is not driven in low temperatures, and if it ever is, it will most likely be above 0F. So I am basically looking for a fluid that provides adequate protection under this light duty cycle and any possible MPG benefits from reduced friction during short to medium distance driving. In my quest to compare the available fluids, I put together the following table based on current PDSs, with fluids listed lightest to heaviest at 100C:

Code:
Fluid			100C, cST	 40C, cST	Viscosity Index

Mobil 1 LS		14.6		103		146
Castrol Syntrax		15		111		???
Valvoline SynPower	15.6		100		150
Peak GL-5		15.9		104.7		162
Redline GL-5		16.4		115		155
AMSOIL Long Life	16.6		129.7		137
AMSOIL Severe Gear	16.8		109		167
Royal Purple Max Gear	17.5		119		???


If lower viscosity equals better fuel efficiency (is that a valid assumption?), looking at it on paper, Mobil 1 appears to be in the lead when it comes to overall fuel efficiency due to it having the lightest viscosity at 100C and second to lightest viscosity at 40C, although it is among the lowest VI. If I was planning on moderat towing or occasional mid-high load, mid-high shock runs, I should lean toward RP or AMSOIL (as I understand it, if I was going heavy load/shock, I would bump up to 75W-140 or 85W-140), right?

So based on the information and assumptions above, product availability and price, and testimonials I have read on BITOG, I have decided to go with Mobil 1. Are there any flaws in my reasoning? I am looking for gear oil education as much as a specific product recommendation here.

[As an aside, I found Valvoline High Performance Gear Oil (conventional) to have interesting numbers of 15.47 cST @ 100C, 99.0 cST @ 40C, and a VI of 166, which, if compared to the fluids in the table above, would be the third lowest 100C number, lowest 40C number, and second highest (by 1 point) VI. Maybe it is a viable option with 25-50k drain intervals?]


With your application you could run anything in the grade that's specd in you owners manual, that was reasonable quality when balanced with price.

If it was my vehicle I would indulge myself and just put the Amsoil in and not worry about it until it gets to 100,000 Kms and do a UOA to see how it's going and top off to replace the sample amount.

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#3330182 - 04/01/14 10:31 AM Re: How to match gear oil to application? [Re: NMBurb02]
72te27 Offline


Registered: 07/21/10
Posts: 89
Loc: Kentucky
NMBurb02, do you have the relatively fragile G80 locker in your rear diff like my '03 does? If so, you may not necessarily want the lightest gear oil in grade. They will all work fine, but extreme pressure additives may be a better data point among that group of excellent oils.
I just talked to Dave at Redline and went with his recommendation.
_________________________
'72 Toyota Corolla 1.6
'03 Suburban 5.3
'05 Honda Accord 2.4
'08 Honda Accord 2.4
'11 Honda Accord Coupe 2.4
'11 Mazda 6 2.5

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#3330323 - 04/01/14 01:02 PM Re: How to match gear oil to application? [Re: NMBurb02]
dparm Offline


Registered: 04/19/10
Posts: 12570
Loc: Chicago, IL
The Peak and Amsoil Severe Gear have the highest VIs. That's a good thing in a differential, as MolaKule has pointed out before. I would use either of those two -- perhaps the Amsoil since it is a tad thicker.

Have you ever considered Renewable Lube's 75w90? They sell it directly on Amazon for $16/qt, and it qualifies for free shipping.
http://renewablelube.com/TDS/4C3-Bio-SynXtra%2075W90%20GL-5%20LS%20Gear%20Oil.pdf
_________________________
2011.5 BMW M3 saloon ZCP
der stärkste buchstabe der welt
Castrol Edge Professional TWS 10w60 + Mahle OX 254D3

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#3330376 - 04/01/14 01:59 PM Re: How to match gear oil to application? [Re: dparm]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1362
Loc: Crowntown, CA
Originally Posted By: dparm
The Peak and Amsoil Severe Gear have the highest VIs. That's a good thing in a differential, as MolaKule has pointed out before. I would use either of those two -- perhaps the Amsoil since it is a tad thicker.

Have you ever considered Renewable Lube's 75w90? They sell it directly on Amazon for $16/qt, and it qualifies for free shipping.
http://renewablelube.com/TDS/4C3-Bio-SynXtra%2075W90%20GL-5%20LS%20Gear%20Oil.pdf

Tempting...it fits right between the Valvoline and Peak in terms of viscosity at 100C (15.7) and blows them all away in viscosity at 40C (90) and VI (187?!?). Also, it says it is "designed to meet/exceed the SAE J306 and SAE J2360 requirements for...differentials (including limited slip (LS) units)...". After some additional research on BITOG (what a novel idea!) and reading a lot of what dnewton has to say on the topic of gear oils, I have decided to go with a J2360 gear oil. Although no Renewable Lube gear oils are on the official J2360 list, are they reputable enough that if they say it was designed to meet/exceed those requirements, we can safely assume that it does?

If I use up some of my stash of G-Oil 5W-30 in the engine and pick up a tube of Renewable Lube chassis grease on Amazon, I'll be rolling in a bio-based renewable base stock full size SUV...won't make me feel so guilty about 13 mpg.

However, the estimated ship time is 2 to 4 weeks so I would need to order it today in order to make sure it arrives before the big trip...

Why'd you have to go and complicate things like that?
_________________________
2002 Chevy Suburban 1500, G-Oil 5W-30, Napa Gold FIL 4805
2006 Pontiac Grand Prix GT, Valvoline ML NG 10W-30 +MMO, Puro PureOne PL10111

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