15K Analysis of Redline 75W90 Diff Oil
Joined: Oct 2009
Posts: 29,896
Likes: 5,437
From: Ontario Canada
james0933, that's not a bad combo. The Red Line Oil Shockproof (which weight?) uses a solid-form of molybdenum (disulphide?) and should be the best at guarding wear under high, high load conditions.
JFusion, I'm a BITOGer so I'm not against testing and short drains ... but 3,000 miles on gear oil? I would say anything would perform well in that amount of time. It takes many thousands of miles and (really) multiple samples to spot wear clear trends using UOAs. With the way most of us do it, it leaves so much open to guessing. I've been OK with that in the past ... but even engine oil at 3,000 looks good 90%+ of the time.
I guess what I'm saying is that if you are going to swap diff fluids every 3,000 miles, I'd go with whatever you can get for $3-5 per quart.
JFusion, I'm a BITOGer so I'm not against testing and short drains ... but 3,000 miles on gear oil? I would say anything would perform well in that amount of time. It takes many thousands of miles and (really) multiple samples to spot wear clear trends using UOAs. With the way most of us do it, it leaves so much open to guessing. I've been OK with that in the past ... but even engine oil at 3,000 looks good 90%+ of the time.
I guess what I'm saying is that if you are going to swap diff fluids every 3,000 miles, I'd go with whatever you can get for $3-5 per quart.
Hey Bror, I've been following your posts for years on BITOG , your name is very distinguishable
, nice to see you made your way over here and have an S2000 , that is awesome. In my case I drained Amsoil 75w110 last season and it did not look good coming out, I sent it out for a sample and it got lost in the mail. I had a bit of a panic and put in Amsoil 75w140 so I want to see how it makes out after a run this season, like you I don't put many miles on the car but I want to sample it once a year regardless right now just to settle my nerves. If it comes back as being a good run then it may settle my nerves and I can do longer runs after that. The idea of dumping out perfectly good fluid on a short run doesn't bother me, it's only a few bucks, I would never run a cheaper fluid just based on dumping it early unless it was a proven to be a good fluid. I'm a bit of an Amsoil fan as well so I want to stick with their fluids unless I find there is an issue with it. I know what you are saying but you'll never get that through my fat hard-headed OCD skull.
I'd also like to see more samples of diff fluids from our cars, we've seen a lot of engine oil UOA's but not many diff samples.
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Joined: Jul 2009
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From: Capital Region, NY
Glad to see you didn't take it personally JFusion, because it wasn't meant to be.
I'm not criticizing anyone for being OCD about oil ...
"Hello Pot, this is kettle, come in pot."
... it's just that UOAs are limited even under normal (full interval) circumstances. Problem is, they aren't precise enough to divine much from a 3,000 miles sample of gear oil. Gear oils typically go 50,000 - 100,000 miles in differentials because only performance enthusiasts are picky enough to change their oil much more frequently than that.
When you get a result of 10-20ppm ... how much of that is due to your current wear ... versus what was left behind from the prior fill (this application has no filter) and how much is in the gear oil from the blending plant? I would think a typical gear oil, with its sulfur-phosphorous chemistry would be more likely to pick up a few PPMs from rusty pipes at the plant before it is bottled.
The problem with good testing is that it is time consuming and/or expensive. These UOAs are not terribly precise and not much can be gleaned from a variance in a couple PPMs. Their best use is in showing trends over time (good or bad).
And then there is lab error. I don't think I would trust a report that came back and showed a gear oil had sheared down 1-2 cSt in 3,000 miles unless they were all at a track somewhere.
I'll still look at your low, low mileage UOAs if/when you post 'em but I don't know what I'll be able to learn from them. I guess we'll see.
I'm not criticizing anyone for being OCD about oil ...
"Hello Pot, this is kettle, come in pot."
... it's just that UOAs are limited even under normal (full interval) circumstances. Problem is, they aren't precise enough to divine much from a 3,000 miles sample of gear oil. Gear oils typically go 50,000 - 100,000 miles in differentials because only performance enthusiasts are picky enough to change their oil much more frequently than that.
When you get a result of 10-20ppm ... how much of that is due to your current wear ... versus what was left behind from the prior fill (this application has no filter) and how much is in the gear oil from the blending plant? I would think a typical gear oil, with its sulfur-phosphorous chemistry would be more likely to pick up a few PPMs from rusty pipes at the plant before it is bottled.
The problem with good testing is that it is time consuming and/or expensive. These UOAs are not terribly precise and not much can be gleaned from a variance in a couple PPMs. Their best use is in showing trends over time (good or bad).
And then there is lab error. I don't think I would trust a report that came back and showed a gear oil had sheared down 1-2 cSt in 3,000 miles unless they were all at a track somewhere.
I'll still look at your low, low mileage UOAs if/when you post 'em but I don't know what I'll be able to learn from them. I guess we'll see.
Joined: Oct 2009
Posts: 29,896
Likes: 5,437
From: Ontario Canada
Glad to see you didn't take it personally JFusion, because it wasn't meant to be.
I'm not criticizing anyone for being OCD about oil ...
"Hello Pot, this is kettle, come in pot."
... it's just that UOAs are limited even under normal (full interval) circumstances. Problem is, they aren't precise enough to divine much from a 3,000 miles sample of gear oil. Gear oils typically go 50,000 - 100,000 miles in differentials because only performance enthusiasts are picky enough to change their oil much more frequently than that.
When you get a result of 10-20ppm ... how much of that is due to your current wear ... versus what was left behind from the prior fill (this application has no filter) and how much is in the gear oil from the blending plant? I would think a typical gear oil, with its sulfur-phosphorous chemistry would be more likely to pick up a few PPMs from rusty pipes at the plant before it is bottled.
The problem with good testing is that it is time consuming and/or expensive. These UOAs are not terribly precise and not much can be gleaned from a variance in a couple PPMs. Their best use is in showing trends over time (good or bad).
And then there is lab error. I don't think I would trust a report that came back and showed a gear oil had sheared down 1-2 cSt in 3,000 miles unless they were all at a track somewhere.
I'll still look at your low, low mileage UOAs if/when you post 'em but I don't know what I'll be able to learn from them. I guess we'll see.
I'm not criticizing anyone for being OCD about oil ...
"Hello Pot, this is kettle, come in pot."
... it's just that UOAs are limited even under normal (full interval) circumstances. Problem is, they aren't precise enough to divine much from a 3,000 miles sample of gear oil. Gear oils typically go 50,000 - 100,000 miles in differentials because only performance enthusiasts are picky enough to change their oil much more frequently than that.
When you get a result of 10-20ppm ... how much of that is due to your current wear ... versus what was left behind from the prior fill (this application has no filter) and how much is in the gear oil from the blending plant? I would think a typical gear oil, with its sulfur-phosphorous chemistry would be more likely to pick up a few PPMs from rusty pipes at the plant before it is bottled.
The problem with good testing is that it is time consuming and/or expensive. These UOAs are not terribly precise and not much can be gleaned from a variance in a couple PPMs. Their best use is in showing trends over time (good or bad).
And then there is lab error. I don't think I would trust a report that came back and showed a gear oil had sheared down 1-2 cSt in 3,000 miles unless they were all at a track somewhere.
I'll still look at your low, low mileage UOAs if/when you post 'em but I don't know what I'll be able to learn from them. I guess we'll see.
It's all good.
The last drain of my diff showed a lot of build up around the drain plug and the fluid looked poorly, so I'm trying to determine if it was doing some clean up of the prior fluids used by prior owners or if it was the 75w110 causing the issues. That fluid was only in for one season so I expected it to come out much cleaner. Unfortunately the sample never made it to the lab somehow.
I was also pretty curious about your 80w90, that sounds very interesting and would be niced to see under a UOA. Thanks for the replies on this.
Joined: Oct 2009
Posts: 29,896
Likes: 5,437
From: Ontario Canada
With a magnetic drain plug on the diff it is kind of like the canary in the coal mine, it is a good indicator if things are getting worse. But what happened with me when changing fluids you never really know if it is immediate wear or cleaning up of old fluids and sludge. That's why a sample of the same fluid over a couple samples is needed.
Croc, I think the outright iron numbers on this sample would be horrible in certain circumstances, but if it is wear left over from break-in then it might be reasonable given the number of times the diff fluid was changed, so a further sample would be helpful to know what exactly is going on. It might be fine on the next sample if wear numbers drop considerably.
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