Should I switch to 75w-140 gear oil?

[davison0976]

Hello Friends Bitogers!

One of my household vehicles Infiniti G37x has a front differential located so close to the engine that you can't insert a hand between the two. Given such a proximity of the heat source would it be advisable to use 75w-140 grade gear oil, especially in the summer?

Manual calls for 80w-90 in both differentials. Interestingly, and as a side note, for Sport model manual specifies synthetic 75w-90, even though it's the same differential as far as I can find.

Currently running Amsoil Severe Gear (SVG) 75w-90 in both front and rear. I did experience seepage in front differential, but it turned out to be a torn outer edge of the seal that allowed dirt to get in, thus affecting the seal of the inner lip.

Any input is much appreciated.

 

[zrxkawboy]

I would continue with the Amsoil 75W90.

 

[Doog]

Originally Posted By: zrxkawboy
I would continue with the Amsoil 75W90.


+1 Amsoil is pretty good.

 

[aquariuscsm]

Don't go thicker than spec in the diffs. Stick with a 90 wt. Mine specs 80W90 (rear diff/RWD) and I use Amsoil AGL 80W90.

Anyone know the actual differences between Amsoil AGL 80W90 and Amsoil SVG? Is it just the weight differences (75W90 vs 80W90) or is the formula vastly different?

 

[davison0976]

Originally Posted By: aquariuscsm
Don't go thicker than spec in the diffs. Stick with a 90 wt. Mine specs 80W90 (rear diff/RWD) and I use Amsoil AGL 80W90.

Anyone know the actual differences between Amsoil AGL 80W90 and Amsoil SVG? Is it just the weight differences (75W90 vs 80W90) or is the formula vastly different?


From what I understood 80w-90 fluids are conventional, while 75w-90 are synthetic and presumably it's an industry standard, not just related to a specific manufacturer.

 

[OneEyeJack]

So far you have not stated a good reason to go out of spec.

 

[CT8]

For differentials thicker is better ,too thick wastes power. On my 96 Toyota I went to 75w-140 because I had some left over from my wifes Superduty pickup I couldn't tell ant difference in feel or Mpgs.

 

[davison0976]

Originally Posted By: OneEyeJack
So far you have not stated a good reason to go out of spec.


I came across this chart in the FSM for the vehicle. It seemed to me that given the proximity to the engine operating at 212F or so, front differential is in 104+F temperature environment.

 

[aquariuscsm]

I tried 75W140 in my car one time and it really seemed to cause alot of drag.

 

[davison0976]

And this is what other page of the same FSM has. I am confused.

 

[davison0976]

From what I gather there is no harm in running 75w-140 except for potential power loss feel. I'll give it a try since I already have 1qt of Amsoil SVO and it's not too early to service the differentials.

Thank you all for the input!

 

[clinebarger]

The only time I have overcome 75w90 syn gear-oil is towing my big 5th wheel in Colorado, The 11.5" AAM survived it....But burnt the paint right off the diff cover. I cant imagine your front diff being in the same conditions?

 

[spk2000]

What about a Frankenbrew combining the 2?

 

[shanneba]

Red Line makes a 75w-110 diff fluid.

http://www.redlineoil.com/product.aspx?pid=147&pcid=4

API Service Class GL-5+
SAE Viscosity Grade (Gear Oil) 75W110
Vis @ 100°C, cSt 20.9
Vis @ 40°C, cSt 131
Viscosity Index 184
Pour Point, °C -42
Pour Point, °F -44

 

[Greasymechtech]

Amsoil, Redline, Driven... make a 75w110. I'd use it in both diffs. I'd also get a good synth for the transfer case...

 

[DrAdmin]

did change to amsoli 110 in my g37x; no diff in feel vs 90 - just more protection. btw: front diff almost idle in this car

 

[davison0976]

Haven't noticed any drag after installing 75w-140 in front differential.

After replacing the oil seal the seepage around the axle appeared to had stopped. Nevertheless, the area at the bottom of diff cover still looked a little oily even after it was carefully cleaned before. That prompted me to think that Amsoil 75w-90 is getting too thin because I did not experience the same issue with stock 80w90 before. That's what prompted me to look into using a heavier gear oil.

The suggested 75w-110 might had been sufficient, but I already had 75w-140 on hand. Will keep monitoring if the area gets oily again.

 

[dailydriver]

Originally Posted By: DrAdmin
did change to amsoli 110 in my g37x; no diff in feel vs 90 - just more protection. btw: front diff almost idle in this car


Does the bolded above mean that it almost never goes into AWD, or did you disable the drive to the front somehow?

 

[davison0976]

Originally Posted By: dailydriver
Originally Posted By: DrAdmin
did change to amsoli 110 in my g37x; no diff in feel vs 90 - just more protection. btw: front diff almost idle in this car


Does the bolded above mean that it almost never goes into AWD, or did you disable the drive to the front somehow?

The way it works on G37x (AWD model) is that the system operates full time in rear wheel drive only mode. It engages front wheel drive only if slippage is detected.

The idea from what I'd read is to give it a true rear wheel drive sports sedan type of performance. Also, front axle was moved closer to the front to keep engine's center of mass behind it for better cornering capability.