Lab test results of five 75w90 gear oils

[Bowtieluvr]

PDSC is an oxidation metric. Higher is better. Brookfield is viscosity, lower is better. 4-ball wear test is low-load equivalent, similar to highway driving; 4-ball weld test is a high-load test similar to shock loading or drag racing.

TL;DR- all of these gear oils are VERY good; some are a little better at certain things, but if you bought one there’s not much lost by waiting to drain for another choice. View attachment 152093

Thanks for sharing this data!

 

[MSCH]

the beauty of all of this testing is it is pretty much useless. the most reliable mechanical part of the driveline is the diff, and most people will never wear one out. LOL... even if they never change the gear lube... so the scientific guys who like to bench race the subject really must be bored to tears trying to prove one synthetic gear lube is going to outperform just about any other in the same viscosity and rating..

 

[SubieRubyRoo]

How much would it cost you to get an additional oil tested?

Which gear oil are you looking to test? It’s possible the data has already been collected.

 

[SubieRubyRoo]

the beauty of all of this testing is it is pretty much useless. the most reliable mechanical part of the driveline is the diff, and most people will never wear one out. LOL... even if they never change the gear lube... so the scientific guys who like to bench race the subject really must be bored to tears as one synthetic gear lube is going to perform just about any other in the same viscosity and rating..

Gear oils & relative performance testing have no value whatsoever. Got it. You do realize gear oils are used in more things than just differentials, right?

So what are you telling this poor sap that their problem is?

 

[The Critic]

Which gear oil are you looking to test? It’s possible the data has already been collected.

Valvoline 75W90.

 

[MSCH]

Gear oils & relative performance testing have no value whatsoever. Got it. You do realize gear oils are used in more things than just differentials, right?

So what are you telling this poor sap that their problem is?

in a nutshell one brand of a comparable gear lube versus another performs pretty much the same.. you can test em all you want, and bench race them to death but in service it just doesn't make much difference.

without doing failure analysis, how can a person know if the poor fellow with the gear problem was caused by lubrication or not some other factor such as abuse, overload etc?

 

[SubieRubyRoo]

Valvoline 75W90.

I’ll see if it’s been tested recently.

 

[SubieRubyRoo]

in a nutshell one brand of a comparable gear lube versus another performs pretty much the same.. you can test em all you want, and bench race them to death but in service it just doesn't make much difference.

without doing failure analysis, how can a person know if the poor fellow with the gear problem was caused by lubrication or not some other factor such as abuse, overload etc?

The data shows they’re clearly not the same. I saw some third-party test results on gear lubes in NASCAR rearends that showed a 2HP difference between 2 “identical” grade gear oils. Even a 2HP reduction in friction and heat will have an impact on performance. That’s 1500W of heat no longer being added to the fluid or parts!

 

[MSCH]

lab testing is one thing, real world testing will indicate another.

Question for you? How many differential have you worn out or replaced in your lifetime?

 

[FordFETruck]

the beauty of all of this testing is it is pretty much useless. the most reliable mechanical part of the driveline is the diff, and most people will never wear one out. LOL... even if they never change the gear lube... so the scientific guys who like to bench race the subject really must be bored to tears trying to prove one synthetic gear lube is going to outperform just about any other in the same viscosity and rating..View attachment 155742

What rig is that dropped out of? I drive terminal tractors for a living and have been driving one for 3 years that sounds like a WW II dive bomber when I let off the throttle - noise goes away when throttle is applied. I've put 33,000 miles on it like that still haven't broke it. I'd say it definitely lost its pinion bearing preload. Showed up like that on a totally refurbished Ottawa Y30.

 

[Pablo]

lab testing is one thing, real world testing will indicate another.

Question for you? How many differential have you worn out or replaced in your lifetime?

Just one.

Before I was an Amsoil dealer. I think around 1998.

I cannot say it was a fluid failure, but the timing was odd. In fact I even doubt it was the gear oil. I changed to Redline. Two months later it grenaded. Please don't carry on about how Redline couldn't have caused the failure. Not worth the effort, because either way we will never know.

 

[MSCH]

Just one.

Before I was an Amsoil dealer. I think around 1998.

exactly... I too have had one fail.. and it wasn't because of gear lube but because it was a 1500 series truck that spent most of its time overloaded and I know no one ever changed the diff lube.. it still held up for 150,000 miles or so. . At least that was how I thought of it. starts off as a little whine, on curves.. then it gets progressively louder over a long period of time... and finally it breaks.

Diffs do wear out, but it isn't one of those things that wears out very quickly... most often it never happens before the rest of the vehicle, no matter what.

 

[SC Maintenance]

PDSC is an oxidation metric

So from the chart, does this mean the first one on the list - Differential Life CC - would last the longest most likely?

 

[MSCH]

What rig is that dropped out of? I drive terminal tractors for a living and have been driving one for 3 years that sounds like a WW II dive bomber when I let off the throttle - noise goes away when throttle is applied. I've put 33,000 miles on it like that still haven't broke it. I'd say it definitely lost its pinion bearing preload. Showed up like that on a totally refurbished Ottawa Y30.

that there is the Diff and axle assembly from NABI Transit Bus... its either a 38 or 44000 lbs Meritor Diff with 5.38 gearing.( I forget which).
Diff failures in a city bus which is subjected to thousands and thousand of acceleration and deceleration load cycles were past 300k miles on average. And all these buses had a retarder, which back loads the diff on deceleration...

Back in the day when we used traditional gear lube diff would last maybe 100k before they got so noisy we knew they were going to break... but when we switched to synthetic gear lube in the early 90's diff started lasting about triple what they did on conventional oils.

In he early days of using synthetic gear lubes, for the most part it was Mobil products, probably because they were easiest to obtain, but over the years they started buying different brands as they came on market and became cheaper.

I know over the years I saw gear lube in the shop from Mobil, Castrol, Petro Canada, BP and a few others I cant recall..
but the rate at which Diffs wore out never changed that I could see.

IMHO the brand of synthetic gear lube just doesn't matter.

speaking of doing the diff replacement job in a bus, we had an attachment for a large cherry picker where we could replace the diff without dropping the axle, and we did it that way once in awhile just because some of the dummies thought it would be easier, but most of the time it was just easier to drop the whole axles assembly to the ground and use the cherry picker at floor level to get the diff installed in the axle housing.. The newer stuff doesn't have a gasket, they use RTV... problem with doing it in the bus was the diff was such a tight fit into the housing you had a good chance of the RTV getting messed up before you got the diff in the axle housing..
plus it was just way easier to do this at body level instead of trying to wrestle with the pumpkin over your head up and torque all that large stuff.

 

[Pablo]

So from the chart, does this mean the first one on the list - Differential Life CC - would last the longest most likely?

Directly from the ASTM link:

"It may be used for research and development, quality control, and specification purposes. However, no correlation has been established between the results of this test method and service performance."

 

[RDY4WAR]

I'm a drag racer. Grenading rear ends is just par the course. lol One of them was likely lubricant related. I was riding with a coworker in the oil patch when the rear end of the company truck spilled its guts all over I-40 at 70 mph. The diff cover was shattered and chunks of of the pinion were scattered across the interstate. Most of the metal was blue and extremely hot with very little oil slick anywhere, only a wad of sludge in the case. My brother, who was terminal manager for the company at the time (later became CEO), contacted the maintenance shop to get the gear oil records and found that they had never changed the gear oil in any of the company vehicles. That truck had ~300k miles IIRC. That's a neglect issue though, not the fault of the oil.

The other rear ends I've destroyed was because I was putting 600+hp through a 7.5" 10 bolt. I'm surprised it lasted as long as it did.

 

[FordFETruck]

I'm a drag racer. Grenading rear ends is just par the course. lol One of them was likely lubricant related. I was riding with a coworker in the oil patch when the rear end of the company truck spilled its guts all over I-40 at 70 mph. The diff cover was shattered and chunks of of the pinion were scattered across the interstate. Most of the metal was blue and extremely hot with very little oil slick anywhere, only a wad of sludge in the case. My brother, who was terminal manager for the company at the time (later became CEO), contacted the maintenance shop to get the gear oil records and found that they had never changed the gear oil in any of the company vehicles. That truck had ~300k miles IIRC. That's a neglect issue though, not the fault of the oil.

The other rear ends I've destroyed was because I was putting 600+hp through a 7.5" 10 bolt. I'm surprised it lasted as long as it did.

Here's a picture of neglect. I am sure that was the OE 1964 factory fill with 159,000 on it. It was like a varnish and super hard to get off everything it touched, and it stained everything. Didn't even smell like gear oil anymore. I almost took it on a 330 mile round trip but decided not to go and put my new posi and gearset in instead. It took 2 hours to clean the baked on sludge out of the axle housing. I sure hope none of these modern gear oils turn into this if left in for a lifetime.

 

[Brice]

Interesting thread. So after reading two pages I'm safe to use whatever 75W90 synthetic gear oil? Manual calls for 75W85 in the rear and 80W90 in the front. Dana M210/M220 with electric lockers.

 

[SubieRubyRoo]

I just wonder about some of you guys. When there’s no data present to show that a lubricant is objectively better or different, y’all yell “there’s no proof that your YY oil is any better than my ZZ oil! Gimme data!”

Then, when presented with data, these same folks quickly pivot to “well I’ve NEVER seen any one of ‘abc’ fail regardless if YY is better!”

 

[RDY4WAR]

I just wonder about some of you guys. When there’s no data present to show that a lubricant is objectively better or different, y’all yell “there’s no proof that your YY oil is any better than my ZZ oil! Gimme data!”

Then, when presented with data, these same folks quickly pivot to “well I’ve NEVER seen any one of ‘abc’ fail regardless if YY is better!”

So long as their ZZ oil is cheaper than that YY oil, it will always be the best thing to ever exist and nothing will change their mind. "Make YY oil cheaper than ZZ oil, then I'll accept it as better."