Want to make sure Im buying correct gear oil for differentials

[Shtiv]

Going to be changing the oil in the differentials coming up. This is the first time changing gear oil and Want to make sure this is what you guys would recommend. I have read a bit about it, but want to double-check. Thanks for your input. Looking at
Mobil 1 75W90 Synthetic Gear Oil

 

[wjburken]

Going to be changing the oil in the differentials coming up. This is the first time changing gear oil and Want to make sure this is what you guys would recommend. I have read a bit about it, but want to double-check. Thanks for your input. Looking at
Mobil 1 75W90 Synthetic Gear Oil

View attachment 270462

What do you have for a vehicle? Pretty sure the AWD front diffs take 75W90, but I think the 4WD front diffs take 80W90.

Am thinking the rear axle takes 75W90.

Check your owners manual.

 

[Shtiv]

What do you have for a vehicle? Pretty sure the AWD front diffs take 75W90, but I think the 4WD front diffs take 80W90.

Am thinking the rear axle takes 75W90.

Check your owners manual.

Sorry, it was in my signature, but looks like it disappeared. 2002 Yukon Denali 6.0

 

[wjburken]

Sorry, it was in my signature, but looks like it disappeared. 2002 Yukon Denali 6.0

No worries.

Looks like you need 80W90 in front and 75W90 in back.

 

[Shtiv]

Great thank you!

 

[wjburken]

Great thank you!

No problem. Here is a link to your Owners Manual, BTW.
https://my.gm.com/content/dam/gmown...uals/2002/gmc/yukon/2002_gmc_yukon_owners.pdf

 

[HD_LS]

Keep in mind that those thin oils are what they legally have to recommend, because that is what they used during EPA fuel ecomomy qualification tests. That recommendation is not at all based on what oil selection will give you maximum durability and life out of your axles.

 

[Jason in DLH]

Keep in mind that those thin oils are what they legally have to recommend, because that is what they used during EPA fuel ecomomy qualification tests. That recommendation is not at all based on what oil selection will give you maximum durability and life out of your axles.

I really haven’t thought much about the gear oil and have simply used the 75W-90 in the past. But interesting you say this as I am considering 80W-90 for my front diff. Or are you talking something like 90W-140?

What do you use?

 

[wjburken]

Keep in mind that those thin oils are what they legally have to recommend, because that is what they used during EPA fuel ecomomy qualification tests. That recommendation is not at all based on what oil selection will give you maximum durability and life out of your axles.

What do you use?

I am not going to deny that GM takes overall fuel efficiency into account when they design the drive train and make fluid viscosity selections. That being said, I have heard of very few people that have had an issue with running the recommended fluids if they use quality products and change the fluids out on a proper schedule. I’m willing to bet that most failures are due to folks not paying attention and letting the fluids go way past the recommended service interval. I would never recommend that folks deviate from recommended viscosity, but would recommend using quality product and doing proper maintenance at recommended intervals. There are a number folks on here that have 200K or 300K on their vehicles that use the “legally required” recommended fluids in their vehicles.

 

[Bill 1960]

Well said @wjburken . It’s also true that friction generates heat, and I don’t believe running a gearbox at a higher temperature, with more drag will extend the life of the internals.

If anyone is really curious, just measure your differential temperature after driving a test course, then swap out the recommended fluid for some aftermarket super juice and repeat. Have I done that? Yes.

 

[Jason in DLH]

I am not going to deny that GM takes overall fuel efficiency into account when they design the drive train and make fluid viscosity selections. That being said, I have heard of very few people that have had an issue with running the recommended fluids if they use quality products and change the fluids out on a proper schedule. I’m willing to bet that most failures are due to folks not paying attention and letting the fluids go way past the recommended service interval. I would never recommend that folks deviate from recommended viscosity, but would recommend using quality product and doing proper maintenance at recommended intervals. There are a number folks on here that have 200K or 300K on their vehicles that use the “legally required” recommended fluids in their vehicles.

I hear you. I have 140K and everything is looking good so far with the recommended viscosity (minus a recently cracked axle housing).

 

[Jason in DLH]

Well said @wjburken . It’s also true that friction generates heat, and I don’t believe running a gearbox at a higher temperature, with more drag will extend the life of the internals.

If anyone is really curious, just measure your differential temperature after driving a test course, then swap out the recommended fluid for some aftermarket super juice and repeat. Have I done that? Yes.

Interesting...how much difference was the operating temp between the two?

 

[HD_LS]

I run Amsoil Synthetic Severe Gear 75W-140. You want to keep the lower number at 75, for great fluidity in cold temps. They've had a number of tests done showing their 75W-140s superior flow at cold temps, and yet they have high film strength at higher temps. Not to mention the lowest wear in various tests.

Lowest running temperature = best fuel economy. Because lowest heat generated = lowest power loss. This is exactly what GM tests for to get best fuel economy. So if you find an oil that generates the lowest temperatures, you have found the best fuel economy oil.

To find the oil that results in the longest life and lowest wear is a completely different set of tests.

 

[Shtiv]

Well said @wjburken . It’s also true that friction generates heat, and I don’t believe running a gearbox at a higher temperature, with more drag will extend the life of the internals.

If anyone is really curious, just measure your differential temperature after driving a test course, then swap out the recommended fluid for some aftermarket super juice and repeat. Have I done that? Yes.

Thank you for the discussion and replies. Are we saying that this Mobile 1 will work fine??

 

[wjburken]

Thank you for the discussion and replies. Are we saying that this Mobile 1 will work fine??

Yes - You should be good to go with Mobil 1.

 

[Shtiv]

Also, I cannot find 80W-90 "SYNTHETIC" gear oil for front diff anywhere.......???? 75W-90 no problem to find

 

[Jason in DLH]

Amsoil carries it...

https://www.amsoil.com/p/severe-gear-80w-90-agl/?code=AGLPK-EA#pills-home_0

 

[Jason in DLH]

Speaking of Amsoil...why in the world is it so expensive?! Are they simply upping their prices to make people think it’s superior than other companies? Or is it just really that good?

 

[Shtiv]

I run Amsoil Synthetic Severe Gear 75W-140. You want to keep the lower number at 75, for great fluidity in cold temps. They've had a number of tests done showing their 75W-140s superior flow at cold temps, and yet they have high film strength at higher temps. Not to mention the lowest wear in various tests.

Lowest running temperature = best fuel economy. Because lowest heat generated = lowest power loss. This is exactly what GM tests for to get best fuel economy. So if you find an oil that generates the lowest temperatures, you have found the best fuel economy oil.

To find the oil that results in the longest life and lowest wear is a completely different set of tests.

I assume this can be used front and back????

 

[Jason in DLH]

I assume this can be used front and back????

You have to make sure you have limited slip additive for the back if your truck is equipped.