Need a 75w-90 GL-5 for a Torsen-type diff

Messages
11,849
Location
PA
This is for my 2011 RX-8. The only thing I know right now is that I do NOT want Red Line or Royal Purple. I'd use a Mazda fluid, but from what I'm reading they only sell SAE 90 or 80w-90; 75w-90 is permitted but not sold by Mazda. I was looking at Motul Gear 300, but I don't know whether I need a type made for hypoid gears. Any suggestions?
 
Messages
1,101
Location
TX
I'm curious why you won't use Red Line? I run Red Line Lightweight Shockproof in my Miata's Torsen unit. Seems to work well enough. I probably wouldn't run Shockproof in a daily driver, but I'd run their GL-5 gear oil. robert
 

d00df00d

Thread starter
Messages
11,849
Location
PA
Originally Posted By: aquariuscsm
I think the 90W,80W90 is the Mazda spec for your car. I'd use one of the Mazda OEM fluids in either weight.
You are correct! Here's the one thing that makes me hesitate: I live so close to the highway that there's almost no time for the diff fluid to warm up after a cold start. I'm not too worried about that in the summer, but winter is coming and I'd hate to be hitting the highway with stone cold diff fluid almost every day. I figure if 75w-90 GL-5 is still within Mazda's guidelines, that's probably a better call than 80w-90.
 

d00df00d

Thread starter
Messages
11,849
Location
PA
Originally Posted By: robertcope
I'm curious why you won't use Red Line? I run Red Line Lightweight Shockproof in my Miata's Torsen unit. Seems to work well enough. I probably wouldn't run Shockproof in a daily driver, but I'd run their GL-5 gear oil. robert
I ran Red Line transmission and diff fluids in my last car (E36 M3) and was underwhelmed. Friends of mine have had similar experiences with Red Line. We've seen them work okay-to-great at first but degrade quickly. In my car, I liked the equivalent Motul products better. Plus, I was always weirded out by the fact that they and their retailers recommended 75w-90 for the E36 M3. The spec fluid for that car (Castrol SAF-XO) was originally labeled 75w-90, but that was before the viscosity scale was revised. Under the new scheme, it would have been labeled 75w-110, which means Red Line's 75w-90 fluids are a whole grade lower than the spec fluid. When I asked about this, all I ever got was the old "never had a problem" response. More generally, I always prefer products that come from bigger companies and carry explicit manufacturer approvals. I know a lot of people have had huge success with Red Line fluids, and I don't think my few experiences outweigh any of that. I just feel like there's no reason not to go with something I feel better about.
 

d00df00d

Thread starter
Messages
11,849
Location
PA
Originally Posted By: d00df00d
winter is coming and I'd hate to be hitting the highway with stone cold diff fluid almost every day.
To clarify, what I meant here is that I'd rather have a fluid with better cold properties if possible.
 
Messages
1,101
Location
TX
Originally Posted By: d00df00d
More generally, I always prefer products that come from bigger companies and carry explicit manufacturer approvals. I know a lot of people have had huge success with Red Line fluids, and I don't think my few experiences outweigh any of that. I just feel like there's no reason not to go with something I feel better about.
Fair enough. I actually feel the same way in a lot of cases. I wouldn't put their "generic" ATF in my Expedition that calls for Mercon LV even though they claim their fluid is compatible. I'm sure it would work okay, but there's no reason not to run the real deal. Their manual transmission and gear lubes have always worked well for me, though. I'll never fault anyone for wanting to run a fluid that is certified to the right spec! Thanks for the honest answer. robert
 
Messages
24,727
Location
Dallas,Tx USA
Originally Posted By: d00df00d
Originally Posted By: aquariuscsm
I think the 90W,80W90 is the Mazda spec for your car. I'd use one of the Mazda OEM fluids in either weight.
You are correct! Here's the one thing that makes me hesitate: I live so close to the highway that there's almost no time for the diff fluid to warm up after a cold start. I'm not too worried about that in the summer, but winter is coming and I'd hate to be hitting the highway with stone cold diff fluid almost every day. I figure if 75w-90 GL-5 is still within Mazda's guidelines, that's probably a better call than 80w-90.
I'd stick with an 80W. I tried 75W90 M1 when I did my first rear diff change on my car (mine specs 80W90) and it whined really bad. Refilled with 80W90 and no more whine.
 
Messages
9,614
Location
Pennsylbammyvania
Originally Posted By: d00df00d
Originally Posted By: d00df00d
winter is coming and I'd hate to be hitting the highway with stone cold diff fluid almost every day.
To clarify, what I meant here is that I'd rather have a fluid with better cold properties if possible.
Look for one with a very high V.I., like yes, some of the Motul fluids. wink hide
 
Messages
8,598
Location
Florida
I often use Valvoline synthetic 75w90, simply because it is easy to find, and isn't too expensive. It is better than the typical 80w90 or SAE90 found in most factory fills.
 
Messages
2,393
Location
Paradise of Florida
Unless there was a failure, I can't see how a fluid can be underwhelming. Torsen doesn't require anything special. Your ring and pinion does. Never saw safxo above 16cst. Do you have any VOA/UOA data showing safxo as a sae110?
 

d00df00d

Thread starter
Messages
11,849
Location
PA
My apologies -- the originally specced fluid for the E36 M3 wasn't SAF-XO; it was SAF-XLS. The data sheets I have seen indicate a kinematic viscosity of about 20 cSt at 100º C.
 
Top