Mobil 1 75w90

[dieselfan1]

Hello BITOG Community
Long time lurking finally joined . Changing all the fluids in both of my 2018 Silverado 1500's.
Ive got a question about Mobil1 75w90 synthetic gear lube for
changing my diffs. The front specs 75w90, the rear wants 75w85.
Any difference that matters here?
One is bone stock . One is lifted 10.5" running 38" tires.
On the lifted one I'm swapping the rear differential cover for an aftermarket PML cover with drain plug and fill plug and 20 oz. more capacity.
I have a case of this Mobil1 on hand so I want to use it. Its about a year old if that matters.
Is Mobil 1 gear lube any good?
Sure I could run over to the amsoil guy down the road and get some extreme duty but I already have this.
Thanks for your reply

 

[oggb]

Mobil 1 gear lubes are fine general purpose oils and you can run the 75w-90 in place of 75w-85 with zero problems. Even if you have the 75w-90 LS version it is perfectly fine to use in a non-limited slip differential.

Especially considering you already have it on hand I definitely wouldn't go out and buy something else.

 

[tasch72]

Yep you're totally fine running 75w-90 in place of 75w-85, the difference in viscosity would be very minimal.
The late-model FJ Cruisers also have the same situation.

 

[930.engineering]

Ensure you use GL-5 rated oils in your differentials unless your manual says different.
GL-4 may provide insufficient protection. I agree 75W-85 or 75W-90 makes a marginal
difference (e.g. 15 vs 20 mPas at 100°C). Depending on your climate I'd consider running
75W-90 GL-5 in both diffs.

 

[dieselfan1]

Ensure you use GL-5 rated oils in your differentials unless your manual says different.
GL-4 may provide insufficient protection. I agree 75W-85 or 75W-90 makes a marginal
difference (e.g. 15 vs 20 mPas at 100°C). Depending on your climate I'd consider running
75W-90 GL-5 in both diffs.

I'm in Minnesota so I get both ends of the thermometer.
It's rated GL5

 

[ka9mnx]

No, you are fine with your selection. Talking about going off the wall, I'm using 75w-140 in all my vehicles (not Mobil1) of which only 2 were back spec'd for. I would actually suggest 75w-140 for the lifted truck just for the extra load the 38" tires will put on the drive train. M1 is a very good oil just not my preference.

 

[dieselfan1]

I'm thinking the extra 20 oz. will help keep it a little cooler along with the fins on the pan. If nothing else it will look cool.
I'm not afraid to run something else either. My warranty was void at 15,000 miles

 

[RoadDukie]

Hello BITOG Community
Long time lurking finally joined . Changing all the fluids in both of my 2018 Silverado 1500's.
Ive got a question about Mobil1 75w90 synthetic gear lube for
changing my diffs. The front specs 75w90, the rear wants 75w85.
Any difference that matters here?
One is bone stock . One is lifted 10.5" running 38" tires.
On the lifted one I'm swapping the rear differential cover for an aftermarket PML cover with drain plug and fill plug and 20 oz. more capacity.
I have a case of this Mobil1 on hand so I want to use it. Its about a year old if that matters.
Is Mobil 1 gear lube any good?
Sure I could run over to the amsoil guy down the road and get some extreme duty but I already have this.
Thanks for your reply

Welcome to the forum!

 

[xmanjeff]

something you may want to look at with the aftermarket diff cover , gale banks did a video of some of the aftermarket diff covers , and pointed out a few key points and some of the bad points . i strongly urge you to try and look it up
it had to deal with the conformity of the cover to the ring gear and slinging the oil up to the pinion bearing , for proper lubrication

 

[dieselfan1]

something you may want to look at with the aftermarket diff cover , gale banks did a video of some of the aftermarket diff covers , and pointed out a few key points and some of the bad points . i strongly urge you to try and look it up
it had to deal with the conformity of the cover to the ring gear and slinging the oil up to the pinion bearing , for proper lubrication

Ive seen the videos a couple years ago.. Gale Banks is genius.
I've run his tuners on two Duramax diesels with great success.
The problem he discovered is the flat covers like AFE and G2 make the oil cavitate and get hotter. The cover I got is rounded like the stock cover.
I was well aware of this before I ordered mine. BTW the Banks cover costs twice as much as the one I got at around $450 and pretty much looks the same.

 

[alcyon]

My 1989 Toyota is rated for 80W-90 diff oil, I put in M1 SHC 75W-90 and it runs better. I also used it in my previous car M/T gearbox also ran great.

 

[dieselfan1]

Getting ready to shoot a few coats of VHT high temp caliper paint on the new cover. It going to look the same but easier to keep clean

 

[yuthanasia]

my IS350 is spec'd for 75W-85 in the rear, I changed it at 98k with Supertech Synthetic 75W-90 and then again today at 194k, never had a problem. For oil with 80,000 miles on it, it was just yellowish as opposed to clear when new...probably could have gone another 80k easily. I wouldn't worry about the weight it's close enough.

 

[OilUzer]

FYI
Valvoline GL5 Full Synthetic 75W90 is on sale for $9.59 at NAPA till end of May. basically almost same as ST syn regular price which I previously used.
I bought a couple even though I don't need any for a while. I think I went from Castrol to Valvoline to ST ... and next one back to Valvoline. I will have to try M1 maybe next time.

 

[4WD]

used M1 75w90 in 4WD GM’s for 20 years … no worries …

 

[SteveG4]

used M1 75w90 in 4WD GM’s for 20 years … no worries …

Me too. Four times over, I've used M1 75W-90 LS in my 2006 Silverado's rear and front differentials. It's fantastic gear oil that doesn't mind cold weather.

The transfer case gets the fully syn version of ACDelco's AutoTrac II fluid.

 

[userfriendly]

No, you are fine with your selection. Talking about going off the wall, I'm using 75w-140 in all my vehicles (not Mobil1) of which only 2 were back spec'd for. I would actually suggest 75w-140 for the lifted truck just for the extra load the 38" tires will put on the drive train. M1 is a very good oil just not my preference.

Right. I switched to 80W140 in everything for the same reason.