I want to replace my diff fluid what should I get?

It's a Base 91 5-spd 2WD with small tires (205/70-14) and it DOESN'T have a canopy.
I assume it either doesn't have a limited slip or it's pretty warn out. I'll jack it up and rotate the tires by hand to check, really can't believe I haven't done that yet.
I use it for daily driving/work and I try to keep any extra weight out of it to help the MPG's. I don't do much towing or hauling and it will never see off-roading.

I'd like to run thin fluid for the MPG benefits but not at the expense of extra wear.

Considering:

Redline 75W-90
Redline 75-110
Redline Superlight ShockProof
Redline Lightweight ShockProof
http://www.redlineoil.com/Products.aspx?pcid=4

Amsoil Severe Gear 75W-90
Amsoil Severe Gear 75-110
http://www.amsoil.com/shop/by-product/gear-lube/

 

I have run every thing from 85w140 This was a little stiff on those nippy days around 0 F

To 75w90

I run local brands either Wolfs Head or Pitt Penn I just bought it in 5 gallon buckets.

Sold at 2 different vendors I deal with

 

75w90 was what I always ran in the stock axle with no issues. I doubt you will see any difference between regular gear oil and synthetic though. But if you want to run synthetic, my money is on the redline.
And if its a completely stock axle, it does not have an LSD.

 

Wyoming, in another post you said you run Lucas 85W-140 in everything. Was that just your 4WD apps?
Do you just use the standard Dino in the 2WD stuff?




Robert, I haven't found anything that's been replaced with upgraded components yet. So far it's quite the opposite.
Found some of the typical idiotic wiring mods and probably AutoZone parts. Hello China barf


I'll lay strong odds it's still a stock diff. Better for the MPG's anyhow.

 

Back in the Day I added Lucas gear oil additive about one gallon to 3 of gear oil . It got used in everything that took gear oil

4x4 stuff Celica transmissions and rears

With everything being up to date and all new I have not needed to add gear oil to anything .for quite awhile.

Then I am not as ambitious as I might be.

As I think about it unless your doing a 100 mile interstate commute every day I think the cheapest gear oil you can get would be fine.

Where people run into issues is never changing it . I had one women her transmission froze because of all the condensation over the years and never getting hot enough to get it out.

She was told she needed a clutch.

I can`t really say about the fancy synthetic as I myself never used it