Mobil 1 75w90LS

Messages
1,589
Location
NC
I have been using this fluid for about 8 yrs and 160k miles in my 01 blazer. The first 15 it used valvoline with no extra modifier and the chatter was pretty bad. I then added the modifier with the valvoline and chatter went away. When 30k came around i put the M1 in there and have changed it every 50 k. Everything is perfect. I have been reading many other posts talking about diff whine, noise, chatter using the M1. Has anyone else had as good luck with it as i have? Or if you had bad luck, what vehicle. Im wondering if it is just not correct for certain vehicles but okay for GM's
 
Messages
14,778
Location
Illinois
In my 96 Merc GM I used M1 gear lub with very good results. Went 155,000 on the first diff change before I changed it. Still looked great and was very quiet. On my old Ranger I went 130,000 miles before changing it and the same results. Oil was still clear when draining.
 
Messages
2,378
Location
Pennsylvania
I have M1 75W-90 in my Nissan Frontier rear diff. Runs great. Very quiet. Before that, I ran it over 10 years in a full size Chevy pickup, changing it only once. Same thing. Quiet, ran very well, no complaints.
 
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Messages
8,756
Location
RI
I've used Mobil-1 75w90 synthetic gear lube since the '80s and it has never failed me. I hear all the 'stories' about how bad it is. I worried for a bit, but believe its just useless worthless anti-M1 hearsay. The Amsoil gear oil test showed it to be a top notch gear oil. I will continue to use it. Those that use it in a manual tranny will complain about it. GL5 LSD gear oil and synchro'd manuals don't mix too well. Those that are too dumb to add extra LSD additive will complain about it. Its LSD-additive dose is just low enough for worn/tired/weak LSDs. Any tighter diff's will need a little extra additive. Those that are looking to blame their fluid for issues caused by neglect, abuse, OE under-engineering will complain about it. If it works for you stick with it.
 
Messages
177
Location
New Jersey
How does M1 75W-90 do in Subarus? I just bought some for my '07 Outback (30k miles on factory fill) for both front and rear diffs. Note that this is an automatic, front diff lube is separate from tranny lube. 75W-90 GL5 is specfied for both diffs.
 
Messages
228
Location
Happy Valley, PA
Just put some in the rearend of my 05 GMC 2500HD with the G80 Eaton locker seems to be doing well so far! 23,000m on the truck and about 600m on the M1. Alot cheaper than the $30 factory grape juice.
 

jstutz

Thread starter
Messages
1,589
Location
NC
Looks like it seems to do pretty well in a mix of gm diffs. The reason i was asking about the noise and stuff is i also have a suburban with 190k miles that i bought used a year ago and it had 170k on it at that point. When i changed the diff fluid it was very black looking and the buildup on the cover was pretty bad. Its probably safe to say that the previous owners did not ever change it. The suburban has a weird howling type noise that seems to come and go as you are going down the road. I was thinking that the diff was warn and making some noise. Maybe some M1 75w140 would do better in that application. does the 140 have the same amount of LS additive as the 90 weight? Would that fluid be to thick during winter for these diffs?
 
Messages
228
Location
Happy Valley, PA
I don't know about the LS additive, I would guess it was the same. As far as the 140wt, my owners manual states for heavy towing a 140 can be used. I wouldn't think it would be affected by the cold. I thought about adding 1qt of the 75w140 with the 1.5qts of the 75w90 to make a 75w110. But I just used the 75w90 instead.
 
Messages
8,756
Location
RI
A 140wt will definitely be thicker then a 80wt when cold. But, both meet the requirements of SAEJ306 75w and either will work well in your profile locations. Old or noisy diffs usually quiet down with a thicker gear oil. 50:50 mix is another option. http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_Synthetic_Gear_Lubricant_LS_75W-90.asp http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMoMobil1_Synthetic_Gear_Lubricant_LS_75W-140.asp The 140wt does get expensive around here and moves you into boutique fluid like, Amsoil, Redline, RoyalPurple, Schaeffers.... Prior to changing out diff gear oil that is noisy or sounds/feels different, always 1st try an additive LSD additive if you know you have an LSD of some sort. If you have a worn diff and assume the noise might be wear related, you can siphon out 4-8 ounces and add some 'snot' to thicken up the fluid. If it quiets down, definitely move up a weight for your next service.
 
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