Yeah, I was a bit put off by the fact it wasn't 75W90, as per Mazda recommendations.

But would that change anything anyway? I mean, there seem to be a lot of people who change viscosities between winter and summer....?

I'll probably just tell the guy to get it in 75W90 instead.

 

According to the FSM, SAE 75W-90 is the correct viscosity for all season use. SAE 80W-90 can be used only if the temperature never falls below 50 deg F (10 deg C). Why not go with the factory recommendation? 80W-140 is clearly way out of spec for our transmissions.

02 DX Millenium Red

 

I just spent the afternoon filling up the tranny with 2.9q's of MT90.

It's definitely easier to do it Roddimus' way, with a funnel/tube.

Putting it into 2nd is a little easier now, and I notice no gear whine at all 4000-5000rpm.

 

some people change the viscosity of the engine oil, not tranny lube, and most of the time it is done because an engine burns a slight amount of oil, so in the summertime when its warmer they can run heavier weight oil and burn less, but in the winter they have to switch back to a lighter weight oil so they dont kill their starter...

and yes, you just fill it up until it starts to slowly seap out of the fill hole, then plug it and call it good, whenever i do stuff like this i try and get myself access to a lift, it makes things a HELL of a lot easier...

and in my honest opinion royal purple and redline are of the same quality, you can hear it from both sides tho because of loyalties, but they are both top notch lubricants, currently i'm running mt90 in my "fun car" lol... and i wouldn't mess with the viscosity, running a heavier weight could potentially damage things, and even if it doesn't damage anything, it might not work as well as it should due to the higher friction between the lube and moving parts...

 

That's exactly what people on the Miata forum are saying about Redline MT-90. Great at first, then after a few thousand miles, it's just OK.
Royal Purple 75W90 seems to be the gear oil of choice over there(and the RX-7 club), and that's what I'm planning on putting into my P5 this weekend.

 

Some reading:
http://forum.miata.net/cgi-bin/ultim...=015350#000001

http://forum.miata.net/ubb/ultimateb...=014416#000002

 

I don't trust the RP Max Gear 75W90 as a tranny fluid -- the Miata guys are prolly using it in their diffs.

I went with MT90 because I recently installed an SS and read certain things about how they tend to wear out the synchros faster. I thought it was a half decent idea to upgrade to MT90, to add a little extra synchro protection, whether that theory of SSs wearing out the syn's is BS or not.

I didn't bother going with RP because it seems as though it's too much a straight gear oil and not a manual tranny fluid -- unlike MT90. Redline puts additives that benefit all parts of a manual tranny, specifically the synchros. Max Gear might give excellent protection of the bearings and gears, but won't do jack for the synchros IMO -- which are really the only things that seem to "go" on a MT. Besides, when have you ever heard of someone needing to replace the gears in a MT, unless the tranny was faulty to begin with in design or manufacture, or they grind like a ****.

RP says Max Gear can be used in anything from diffs to MTs. Redline doesn't say that MT90 can be used in anything else, other than MTs. For diffs n'such, they sell gear oil.

 

Anyone have any experience with Redline Superlight Shockproof? How about GM and/or Penzoil Syncromesh fluid?