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#3468976 - 08/30/14 01:32 AM Need a 75w-90 GL-5 for a Torsen-type diff
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: 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?
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3468977 - 08/30/14 01:38 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
bdcardinal Offline


Registered: 06/03/05
Posts: 6521
Loc: Santa Barbara, CA
_________________________
2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

Ford/Mazda Parts Counter

NRA Endowment Member

"Fear disturbs your concentration."
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#3468980 - 08/30/14 01:42 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: PA
Perfect. Thanks!

Is this what the Boss 302 uses?
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3468984 - 08/30/14 01:52 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
bdcardinal Offline


Registered: 06/03/05
Posts: 6521
Loc: Santa Barbara, CA
Not sure, my Torsen T2 calls for 75W140.
_________________________
2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

Ford/Mazda Parts Counter

NRA Endowment Member

"Fear disturbs your concentration."
-Sabine Schmitz

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#3468985 - 08/30/14 01:58 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
aquariuscsm Offline


Registered: 12/30/06
Posts: 9752
Loc: South Texas,USA
I think the 90W,80W90 is the Mazda spec for your car. I'd use one of the Mazda OEM fluids in either weight.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#3468986 - 08/30/14 02:02 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
Greasymechtech Offline


Registered: 07/11/14
Posts: 334
Loc: Paradise of Florida
Mobil1, Amsoil, Valvoline, Amalie, Eneos, Smittys, Castrol... ANY full synth GL5 75w90 !!!
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At what point should a lurker start posting :-)

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#3469010 - 08/30/14 05:16 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
robertcope Offline


Registered: 01/10/08
Posts: 529
Loc: 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

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#3469069 - 08/30/14 08:24 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: aquariuscsm]
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: 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.
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3469204 - 08/30/14 11:01 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: robertcope]
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: 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.
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3469208 - 08/30/14 11:03 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: 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.
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3469229 - 08/30/14 11:24 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
robertcope Offline


Registered: 01/10/08
Posts: 529
Loc: 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

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#3469233 - 08/30/14 11:33 AM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: robertcope]
d00df00d Online   content


Registered: 10/20/05
Posts: 9195
Loc: PA
cheers
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#3469384 - 08/30/14 02:43 PM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
aquariuscsm Offline


Registered: 12/30/06
Posts: 9752
Loc: South Texas,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.
_________________________
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Syntec 10W40/Fram Ultra
Amsoil MTG(tranny)
Amsoil 80W90 GL5(rear diff)
Mobil 1 ATF
Redline Water Wetter

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#3469423 - 08/30/14 03:49 PM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
dailydriver Offline


Registered: 03/14/06
Posts: 7015
Loc: Bucks County, Pa.
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
_________________________
2000 Z28 1SC 6 speed 170K miles
Red Line 0W-40/Sustina 0W-20 (80/20 mix)
Amsoil EaO 64 filter
Synpower 75W-140/4oz. XL-3
Ravenol MTF-2

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#3469427 - 08/30/14 03:53 PM Re: Need a 75w-90 GL-5 for a Torsen-type diff [Re: d00df00d]
Greasymechtech Offline


Registered: 07/11/14
Posts: 334
Loc: Paradise of Florida
Warm or cold, as long as it is full synth, I wouldn't worry about cold highway run. M1 worked great in my Mazda diffs without noise.
_________________________
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