85w90 vs 75w90

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746
Location
Tn,USA
Thread starter
This is for front/rear differential for 2000 ml55 amg mercede. Can I use Amsoil 80w90 for front and rear or get 75w90 Amsoil? I know Motul gear 300 is 75w85 is good for rear. But idk. I believe front called for: 85w90 And Rear: 75w85 I'm having hard time choosing what brand of fluids should I go with. Money is not the issue since I only needed total of 3 qts for F/R.
 
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305
Location
Rainville, USA
I'm guessing it specs the same 235.0 85w90 as my clk430 of that generation, if that's the case you can get the liqui moly 235.0 85w90 as speced and approved by MBZ pretty cheaply on Amazon. It's what I've been using for many years and it has served me well. 75w85 is the superseded spec for fuel economy and to standardize with the new cars, but really you just need (and probably want) the stuff they originally called for in those diffs when the ML was new
 
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4,823
Location
VA
Originally Posted by aquariuscsm
Use Amsoil Severe Gear 75W110.
I agree. 110 is what the old 90 was.
 
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13,196
Location
Maricopa Arizona
Originally Posted by Rohan
This is for front/rear differential for 2000 ml55 amg mercede. Can I use Amsoil 80w90 for front and rear or get 75w90 Amsoil? I know Motul gear 300 is 75w85 is good for rear. But idk. I believe front called for: 85w90 And Rear: 75w85 I'm having hard time choosing what brand of fluids should I go with. Money is not the issue since I only needed total of 3 qts for F/R.
If the gear oil meets the proper GL specs for the vehicle you can use what you want to use.
 
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13,196
Location
Maricopa Arizona
Originally Posted by Gebo
Originally Posted by aquariuscsm
Use Amsoil Severe Gear 75W110.
I agree. 110 is what the old 90 was.
Do we know what the viscosity of the factory fill was?
 
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746
Location
Tn,USA
Thread starter
I don't know what was factory fill was but only thing I know is front called for 85w90 and 75w85 for rear. I cannot find those number except liquid moly 85w90 and 75w85 on Motul 300.
 

4WD

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13,503
Location
Texas
Have a front/rear hair splitting difference with my two GM 4WD's … probably since AAM specs the rear and I worry about the Eaton locker parts the most. I just go with Delvac 1 75w90. If it's good enough for HD equipment and the Porsche tracks boys … I don't need no stinking Amsoil SG (and what it costs). Got the D1 for $32/gallon.
 
Messages
305
Location
Rainville, USA
Originally Posted by Rohan
I don't know what was factory fill was but only thing I know is front called for 85w90 and 75w85 for rear. I cannot find those number except liquid moly 85w90 and 75w85 on Motul 300.
Fuchs also makes an approved 75w85
 
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1,962
Location
Seattle-ish, WA
Absolutely run and 80w90 in the front and 75w90 in the rear. No problem. You could really run either, in both. The difference are small and akin to running a 10w-30 vs. 15w-30 engine oil. And in Tennessee, it becomes less of an issue. Climate matters, don't let that "5w-30 everywhere" Mafia cloud your judgement... wink And don't be tempted to go higher on the 2nd number unless you are towing with it a fair bit. Just means more VII's to shear and make a problem. Do check it the rear is LSD and needs additive - that's an issue. If you do in fact have an LSD rear diff, then there's another level of additive and performance-check you need to do. So verify that and ask back. The last time I did a bunch of differentials (2 years ago?), Walmart had a full syn Valvoline 75w-90 for like $7/qt, a real steal. No Idea if it is still around in their inventory.
 
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3,220
Location
West Michigan
So a few years ago I was doing regular drain and fills of a 2014 Explorer's PTU. FIlling involved squirting about 400ml of gear oil through a 16 inch long 3/8" diameter hose which I installed as a breather extension. The first time I used 80w90 that I had laying around as a short OCI "flush". This was in 90 degree August heat. It took FOREVER. Subsequent fills used quality 75w90 synthetic, which while still painfully slow were MUCH faster than the conventional.
 
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13,196
Location
Maricopa Arizona
Originally Posted by Oro_O
The last time I did a bunch of differentials (2 years ago?), Walmart had a full syn Valvoline 75w-90 for like $7/qt, a real steal. No Idea if it is still around in their inventory.
I paid close to this price for DELO 75W90 at AutoZone. I believe the value in is there.
 
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746
Location
Tn,USA
Thread starter
Can someone verify if ml55 came with LSD? From googling online I don't think ml came with lsd only GL Model.
 
Messages
45
Location
CO
I've been challenged recently with Valvoline's decision to remove LSD additive from their 80W-90 gear oil (GL5) that I used in my rear differential. I really want to keep costs down and even adding the additives to each axle will be costly. I noticed the kinematic viscosity of the 75W-90 (does still have the LSD additive in it) is actually higher at 100 degC than the 80W-90 (15.47 vs. 14.5), and the 40 degC viscosity is much lower than the the 80W-90 (expected), at 99.0 vs. 145.9). I'm wondering how the lower viscosity of the 75W-90 at lower temperatures could affect the rear differential operation. Would it be safe to use? Nissan "calls" for a 80W-90 in both front and rear differentials. Anybody know what the kinematic viscosity is for the OEM Nissan fluid (80W-90)? Thanks!
 

Astro14

Staff member
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11,639
Location
Virginia Beach
The thinner viscosity of the 75W90 at lower temperature still gives you an oil hundreds of times thicker than any of them at operating temperature. So, no, I wouldn't worry a bit about using it.
 
Messages
45
Location
CO
Originally Posted by Astro14
The thinner viscosity of the 75W90 at lower temperature still gives you an oil hundreds of times thicker than any of them at operating temperature. So, no, I wouldn't worry a bit about using it.
Thanks for the reply. I figured in most cases there wouldn't be any issue, but I wonder if there is a need to better protect the gears when cold out and instantly starting off in the vehicle in 4WD. I wonder if the reduced viscosity in the cold weather may not support the possible shock loading?
 
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86
Location
Raleigh, NC
The Kv 100 isn't that far off but the KV 40 is a lot lower. I would think this would help gas mileage and responsiveness but am concerned about wear. Anyone have experience to share? I have a 2015 Subaru.
 
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