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Yesterday I changed diff oil.
29101 km, about 2 years, including a 20 lap track day.
After a warm-up drive I drained part of the oil in a glass so I could measure the temp.
I took the temp within minutes after driving.
Max temp was 69C, outside temp was 18C.
This was lower than I expected as I once measured the outside of the diff after a spirited drive at an average of 63C.
This is the amount of iron dust on the magnetic drain plug.
Most of it is paste, a few small flakes and one bigger particle.
The "chuck" is on the right in the middle.
The big flat part is 1 x 2 mm and thinner than the paper its on.
This is how much I could fingerpaint with metal dust.
Much like the first time I did this, right after the 4.57 break in.
Also, doing this I could feel any particle bigger than dust and I went through all of it.
Amsoil SG SAE 190 is dark green when new, the used oil had a bit extra darkish colour but not much.
No burned smell at all.
No "metallic paint" as well, clean and clear oil.
Its possible to see the ring gear through the drain hole.
I waited for the best part of an hour to let all the oil drain out.
Both the drive side and the coast side of the ring gear looked fine, the drive side was actually like a mirror.
No damage, perfect.
I tried to take a picture but the camera would not focus in the dark and deep.
Its hard to get the lens and a flashlight in the same spot.
Conclusion #1: not bad but the OCI was too long.
This fill is getting changed in 10-15k km.
Why?
Well.. because I noticed 2 things after the oil change.
First, the diff made less noise.
The 4.57's are known to be loud, so is mine.
It peaks between 82 and 95 kmh.
With the fresh oil there was noticable less noise at those speeds.
I guess one gets used to noise if it changes gradually.
Second, the handling changed a bit, changed for the better.
1 - The Torsen is a huge part of how the car handles, especially in corners.
2 - Oil has a (huge) effect on how the Torsen behaves.
Combine 1 and 2 and you get: Diff oil can have an effect on handling, especially in corners.
2 week ago I went back to my summer tires - S-02's.
So on dry & warm roads I cornered a bit faster, more spirited
What I noticed is that the car seemed to have a slight bit of understeer, especially half way into a corner.
The turn-in was ok, but staying on the throttle - as you should with an AP1 - halfway into the corner the front would slightly move outwards, as if it was pushed outwards.
Correcting a bit, still saying on the throttle it would disappear towars the corner exit.
After the oil change I took the same route I used to warm up the diff as a test drive.
Thats where I noticed the car was more neutral in corners.
Turn-in was normal but the front would not understeer.
About 4 years ago I had a simular experience.
The dealer changed diff oil and after about 5-6k km I noticed the same behaviour, a bit more to be honest.
First thing I checked was tire pressure = was fine.
Then I figuerd it was the steering rack.
So I went to another Honda dealer, one with more S2000 experience and asked them to check the steering rack.
All they did was change diff oil to Honda Marine SAE 90 GL-5.
Problem solved.
Note: this was with my OEM 4.10 diff.
Conclusion #2: a 4.57 diff needs good oil.
The ring & pinion "chew-up" the oil in such a way it changes the behaviour of the Torsen, in a bad way.
The Torsen relies on good EP qualities to do its work while cornering.
Conclusion #3: this change in handling - for the second time - convinced me even more the modern 90 weight multigrade diff oils are not for the S2000 diff.
Can you get Amsoil SAE 250? I can send you a quart if not.
I use 8 to 10oz in the rear then top with Amsoil 75/140. I find that the 4.57 works well with this blend
I would really like to know your thoughts on the blend if you do try it. I respect your input especially when it comes to your knowledge on lubricants, you are a true asset to the community
I've been running 75w-110 Amsoil SVG, I've been thinking about 75w-140 though
In an OEM diff both should be ok, depending on the OCI the 75W-140 might work a little longer.
The official normal OCI is way too long IMO!
S2KPUDDYDAD Posted on May 30 2010, 04:07 PM
Can you get Amsoil SAE 250?
Yes, the Amsoil dealership in the UK has it.
I use 8 to 10oz in the rear then top with Amsoil 75/140
The diff holds ~ 28 oz right?
Wouldn't that mix be around an SAE 190 at operating temp?
It depends on the actual viscosity.. I'll have to find the specs first. edit:
Amsoil SG SAE 250 = 47.4 cSt @ 100C
Amsoil SG SAE 75W-140 = 25.7 cSt @ 100C
9/28 x 47.4 + 17/28 x 25.7 ~ 30.8 cSt
That would still be an SAE 140, a thick one though.
Btw.. I don't have any real knowledge on lubricants.
Knowledge in the sence that I've studied it or that's my line of work.
IOW I'm not a tribologist.
All I know is from gathered specs on manufacturer's websites and from what I've been reading about oil on BITOG and a bit overhere (Roadrage's posts)
I'm an informed enthousiast at best
So far I'm happy with the SAE 190, I just used it too long.
In my climate the SAE 190 has a good enough cold flow and is thick enough when hot.
But it doesn't get that hot allthough it might at contact point.
INTJ Posted on May 30 2010, 06:28 PM
And chunks? Wow
Well... just the one chunck
You definitely are in the annual replacement club
I hope you mean "Annual oil replacement club"
I forgot to mention my 4.57's now have ~54000 km on them.
We just did a fluid change on a 4.57 rear that had over 20k on the oil. The magnet and oli were very clean like yours, the owner had Amsoil 75/110 oil in the rear.
There is no substitute for quality oli
Oil viscosity has barely if ANY effect over Toque Sensing limited slip differential behaviour. The Torsen is a purely mechanical device; it has no electronics, clutches or viscous fluids, and it has a fixed bias ratio that is based on the gearing. You would have to use a different gearset to change the bias ratio/locking. The thicker oil film CAN modify bias, but this change is very usually very subtle.
And your visual / subjective / isolated results are hardly a strong basis for recommending viscosities; I applaud your efforts but seriously, OEM has done an order of magnitude more and better testing. Unless 4.57 gears behave totally different to 4.1 gears (not likely), or you´re using the car in a racing enviroment (where diff temperatures would be much higher thus viscosity would go down), I´d stay with stock viscosities.
SAE 190 in a 4.57 diff - 29101 km
