Blending Mobil 1 Gear Lube

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Toy4x4runner

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Alright guys... thanks to everyones input and some decision making I've decided to go with Mobil 1 Gear lube in the rear of my F250; which specs 75w-140syn w/3oz LSD additive.

I started looking at viscosity charts and wow, that cleared some things up. That really puts things in perspective. Looks like these gear lubes are running the low/thin end of the spec. and no way am I running straight 75/90 which is basically 40wt motor oil! I got that out of my head, no straight 75/90. Thinnest I'd run is 50/50.

50/50= -20% thinner than compared to straight 75/140 M1.
40/60= -16% ...
30/70= -12% ...
20/80= -08% ...

What do you guys think on a blend % of 75/90 and 75/140? Reason for going thinner is saving fuel!! Diesel is expensive. I don't tow/haul anything normally other than few people and light junk in the bed.
 
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the rear of my F250; which specs 75w-140syn w/3oz LSD additive.

I'll assume that this is a 4x4. They probably spec the 140 for protection while off roading. If you don't off road you MIGHT be able to get away with a thinner oil.

If you off road, go with the 140.

As above, the Amsoil 110 is a good choice if you go that route.
 
my transmission calls for a 75w85, so i made a witchs brew of 4 qt ST 75w90, 2 qt Pennzoil synchromesh which seems to be a 70w80, and 5 qt. mobil 5w30 extended, because mobil says it is safe for yellow metals, and it seems to be similar to a 70w85, along with 1qt. MoS2 colloidal.
the final mix is thinner than the 75w90, and thicker than the 5w30.
I'll report back in a couple weeks, when my mechanic will have installed all of the complete drive train (engine + transmission from wrecker, new clutch). i'll see if anything dramatic or catastrophic happens. When I was pouring the cold 75w90 - it was like molasses, or honey, which i think is not good, but what do i know?
 
Talking about using motor oil in manual transmissions,I read on 3si.org (3000GT/Stealth forum) where they`ve had good results using Mobil 1 15W50 in their manual transmissions. Wonder how that oil converts gear oil-wise to their oem spec`d 75W90 GL4?
 
I was shocked at what supposedly 75w90, semi synthetic at that, pours like when cold. absolute molasses. i imagine that even mobil 1 15w50 would pour better than that. someone called up mobil, and they reported their extended synthetic oil is safe for yellow metals. i think the 15w50 would likely go good for this ford f250 application, with LSD supplement.
 
Go with the Amsoil 110W. No need for a witch's brew of M1. Motor oil isn't gear lube - different additives and base stocks. Viscosity doesn't tell the whole story. DO use LSD additive.

I once thought I would increase my 1/4 mile ET in a drag car using 15w50 motor oil in the rear end (less friction). That 'Bright Idea' cost me over $600 in gear and bearing damage.
 
Originally Posted By: scoobie
I was shocked at what supposedly 75w90, semi synthetic at that, pours like when cold. absolute molasses. i imagine that even mobil 1 15w50 would pour better than that. someone called up mobil, and they reported their extended synthetic oil is safe for yellow metals. i think the 15w50 would likely go good for this ford f250 application, with LSD supplement.


I put a leftover half quart of Mobil 1 15W50 silver cap in the freezer overnight one time and it still shook around in the bottle just fine.
 
over and done with. we're so off topic it's not funny. I'm just dumping in all 75/140 Mobil 1. It already has the Limited Slip additives in the oil so I don't need to add any (unless I still get chatter). Tired of turning this into a science experiment. I thought more folks would have messed around with this stuff when gas was $4+.
 
I don't think you would have really gained any efficiency.

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What are yellow metals? Explain please.


the brass and bronze parts in a transmissions. not an issue with rear ends.
 
As others have indicated, go with Amsoil 75W-110 severe gear oil. No need to mix yourself + you'll get a very high quality gear oil.

Rumple
 
Ok, but is mixing the Mobil 1 75/90 & 75/140 to a 50/50 blend going to damage the oils themselves? IS it safe to mix the same brand but different visc gear lube is my question.
 
I'm curious if you would really get a median viscosity or if it would stay 90 and 140. sort of like if you mixed 1" balls with 1/2" balls you wound not automatically get 3/4" balls.
 
On mobil's website they say it's safe and ok to mix different mobil viscosities... of oil. didn't say anything about gear lubes. Mobil did say not to mix different brands of oil other than for topping off due to the base stock of the oil, or something to that nature.
 
Originally Posted By: scoobie
I was shocked at what supposedly 75w90, semi synthetic at that, pours like when cold. absolute molasses. i imagine that even mobil 1 15w50 would pour better than that. someone called up mobil, and they reported their extended synthetic oil is safe for yellow metals. i think the 15w50 would likely go good for this ford f250 application, with LSD supplement.


The gear oil is only going to be 75 wt. when cold.

I would guess that the flowability of the synthetic component in the synthetic blend is being hampered by the dino in the mix.

Now way it's going to flow like a 15W motor oil.

For the OP, I'd stick with the factory recommended 75W-140 and use a good, readily available synthetic gear oil like M1.
 
10-4 fellers. Didn't know if mixing the oils would be good or not...never done that before. Figure i'm just gonna run the M1 75-140 and put the stock cover back on and call it a day.
 
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