Joystick? Aren't we Mr. Highfalutin all of a sudden?

Ain't no joystick what I remember:





They've got three non GL-5 oil listed under the "Gear Oil for Manual Transmissions" section: MT-90, MT-85, and MTL. 75W90 NS claims GL-5 / GL-6 / MT-1, but not GL-4, yet claims that it's "Designed for transmissions and transaxles" and "Popular in Ferrari, Porsche and Subaru transaxles," presumably because it "Contains extreme pressure additives like our 75W90 GL-5 oil, but lacks friction modifiers to balance slipperiness."

Source: http://www.redlineoil.com/Products.aspx?pcid=7


I understand what's being said here. Everything that's been said is logical. GL-5 is for hypoid gears, and supposedly contains some sort of Extreme Pressure Additive that either bonds to copper or brass parts (rendering the synchro cones unable to do their job) or just attacks and corrodes these parts outright, depending on who you believe.

And Hustler, bbundy, y8s, I'm not calling y'all liars or even that I doubt what you're saying.

I'd just think that if there was a serious risk of damage to the transmission as a result of running GL-5 lube, or even of the shifting performance of the transmission being degraded even slightly, that Mazda wouldn't be slapping a label under the hood of every new Miata telling you that you can run either GL-4 or GL-5 in the transmission. Even if they just suspected that maybe something very slightly bad could possibly happen if you ran GL-5, they'd issue a TSB to have a new sticker put under the hood, in order to avoid the risk of having to deal with warranty claims and bad press.


I just went and looked up the owner's manual for the 2010 MX5 at MazdaUSA:



It's been 21 years now, and they're still making the same recommendation.

source: https://www.mymazda.com/MusaWeb/pdf/...010_MX5_OM.pdf

 

Just out of curiosity I have a torsen diff can I use gl5 in there?

 

Well, both Mazda and all of the major oil manufacturers say that you should, which I guess means not to...

In all seriousness, though, yes- any hypoid differential needs GL-5, regardless of whether it's a Torsen or not. Clucth-type diffs are the only ones with special lube requirements, and that generally comes in the form of a separate additive (such as this or this) which is mixed with the GL-5.

But for Torsen or Viscous diffs, no additives. Just GL-5.

 

i was just looking into all this stuff, thanks for the info guys. sorry dont have much to contribute of my own... i ran MT90 in MS3 lol. It was great, just sucked when cold, but whatever.

 

Anyway you slice it if you don't read the msds of fluids that go into your car you better listen to someone who has. Not the person selling it either.

Another note: I don't know how much I would trust Mazda based on the rate of new NC engine failures and their recommendation of a certain engine oil weight.

 

(didn't leave my house)

I've experienced the "less than stellar" shifting problems associated with using a compatible but imperfect gear oil in my AWD celica which suffers from the front diff being in the same oil as the transmission but since it called for a GL-5, I did what it said. Ran Redline and suffered the notchiness.

In any case, I'm not going to sweat the load rating differences in the miata--it's a daily driver and I want smooov. The GL-5 is getting exchanged for the GL-4. And with Mr Bundy's positive comments, I feel the Amsoil MTG is a sound choice.

 

I use TORCO every where. It rocks and it has been amazing.. Engine is SR5 20/50 and RGO in the gear box and diff..

 

In recent news, NOBODY sells any kind of GL-4 anywhere in this damn town.

Except Finishline and the Sunoco next door to Braineack... which both sell MT-90.