80w90 Differential Oil?

I just rolled over 30K miles and figured it was time to change out my diff oil (front, rear, transfer case). I went to two different stores looking for

$30 Mobil 1 75w90 Mobil 1 104361 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

Mobil 1 75w90 since I've seen several recommendations for it- one didn't carry it (or any 75w90, for that matter) and the other was out of stock, but I did find some Amsoil 80w90 GL-5 on sale.

The guy at the counter swore it would work just fine in place of 75w90. Should I give it a try or shop around a bit more? Has anyone had any experience using a higher weight oil than what the manual calls for? Keep in mind that I live in a pretty warm climate (US deep south) so cold weather isn't a concern.

This is my first time changing the diff oil myself but it looks very easy to get to on the '11. I don't trust any of the shops around here and the dealer wanted $95 per axle!

 

It'll be a lot thicker when it's cold so winter mpg will take a major hit but other than that it'll be fine.

Toyota wanted so much because they'd be (or are supposed to be) using Toyota's 75w85. If you buy it at the dealer, a lot of places it's marked up to over $30/quart.

Personally I hunted down a redline dealer in my area and used their 75w85 at $14/qt. Still not cheap, but I live in the snowbelt and it's worth it up here.

edit: don't use the 75w85 in the xfer case, that's still 75w90. Didn't see you were gonna do that too. All 2009-up owners manuals says 75w85 for the diffs.

 

Service manual says straight 90-weight oil for normal use, and 75W90 for cold climate. 80W90 will be fine.

 

Thanks! I gave it a try and had no trouble changing out all three.
our local dealer didn't even carry it... said that they buy by the drum for their service department, but that I'd have to special order it (I think they wanted $19/quart).

The transfer case drain plug had no magnet, which surprised me... I assume there's no need for one?

 

The transfer case has an oil circulation system with built-in pump and oil passageways. There's a filter on the oil pickup inlet and a built-in magnet, so no need for one on the drain plug.

From this thread: http://www.tacomaworld.com/forum/2nd-gen-tacomas/131275-inside-05-tacoma-t-case.html

 

Do you need to add a additive to the gear lube like you do in the ford rearends

 

you do for sport models with the LSD. . . not the offroads with the locka.