Difference between 85W-90 and 75W-90 gear oil?

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I just did a drain and fill on my 93 beater altima manual transmission. The stuff I pulled out was 75W-90 GL4 from 10 years ago. It was pretty bad.

I replaced it with NAPA sta-lube 85W-90 GL4. That stuff was thick! I'm wondering if it's too thick for the New England winters. My owners manual indicates 75W-90 and 80W-90 are good for +40F to -40F. It lists 85W, but I don't know if that's the same as 85W-90.

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There is no need to change it out. Keep it unless it becomes unbearable.

Shouldn't be too bad. I've used the 85w90 year round. It'll be a tad slow the 1st couple shifts during the couple weeks of the Northeast freeze wave every Jan/Feb. Rest of the year was fine.

A bottle of Lubegard gear oil supplement can make up for the cold stiffness.
 
Originally Posted By: unDummy
There is no need to change it out. Keep it unless it becomes unbearable.

Shouldn't be too bad. I've used the 85w90 year round. It'll be a tad slow the 1st couple shifts during the couple weeks of the Northeast freeze wave every Jan/Feb. Rest of the year was fine. A bottle of Lubegard gear oil supplement can make up for the cold stiffness.


Thanks folks. Any chance this will congeal and provide no protection in say the few days a year it goes below 14F? I really don't want to pull it all out unless I'm causing risk to the transmission.
 
Originally Posted By: unDummy
There is no need to change it out. Keep it unless it becomes unbearable.

Shouldn't be too bad. I've used the 85w90 year round. It'll be a tad slow the 1st couple shifts during the couple weeks of the Northeast freeze wave every Jan/Feb. Rest of the year was fine.

A bottle of Lubegard gear oil supplement can make up for the cold stiffness.





I'm gonna side with you on this, Before you change everything out just wait and see, you should be fine. I have direct experience with the cold and gear-oil even though I live in FL now.
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I did the same thing on my manual Lexus SC300. I put in a oil that was thicker than called for (this is actually a very long story and frustrating, I will not infuriate you with the details) I ended up draining it in the middle of winter in my garage -- VERY COLD! -- and putting in 75W-90. Shifting was a problem on cold mornings, the oil change resolved the issue. I cannot stay that you will have the same problem, but this is my experience.
 
So far so good. It's definitely a bit stiff, but seems ok when it warms up. Contrary to the gear oil spec chart in the OP, I have read that 85W-90 is good all the way to 0F, and this post indicates sta-lube flows pretty good for an 85 weight oil.

BTW, I do see that NAPA also has a GL-3/GL-4/GL-5 80W-90 for $3.29 a quart. I probably should have used that, but I wanted to stick with GL-4 only.

One thing for sure though is that I will have to alter my downshifting habits. I like to downshift a lot and use the engine as a brake. Can't do that if it's too stiff. Maybe I'll take the advice and get the lubegard gear oil additive.

It was down almost a quart, and now shifts much smoother. Hopefully will add life . Would like to get 25 years of service out of this vehicle before sending it off to the crusher
 
Your old oil was beat up and sheared to a thinner viscosity.
Also drained when warm?
So of course the new stuff will appear thicker.

The differences are small between 75-80 and 85-90 [everything else the same].

I am not sure that that particular lube is the best for manual trannys.
Wear should be good, but good shifting is not addressed.
 
I didn't know they made 75w gear oil in 1993.

I think the only difference is cold viscosity. They should both be a 90 weight when up to operating temps. Your 1993 gears are probably loosey goosey, and the heavier oil might be unnoticable or even better.
 
So far so good. After it heats up, it's very nice. Man, I did not realize how shot my old oil was. But those Altima's are rock sold man, despite my lack of education on gear oil changeover. No cheap parts in the transmission like the Honda garbage, so I think it's probably ok, despite the abuse.

With the new gear oil in, it's very smooth. Prior to that, I could not get a smooth transisition between shifts no matter how delicate I was with the clutch. It would always give that knocking sound like when you let the clutch out too fast without accelerating enough. That's what motivated me to do the fluid changeover. Glad I did.
 
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