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GL-4/GL-5 gear oils a compromise? #5385030 03/24/20 11:30 PM
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Bill_W Offline OP
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Been shopping for an alternative to the OEM 75w-90 GL-4 gear oil for my 2019 Miata MT. Aftermarket gear oil has some GL-4 and GL-5 combo in that weight. Am I better off looking at just the GL-4 75w-90 gear oil?


Slick
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385033 03/25/20 12:08 AM
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AC1DD Offline
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Originally Posted by Bill_W
Been shopping for an alternative to the OEM 75w-90 GL-4 gear oil for my 2019 Miata MT. Aftermarket gear oil has some GL-4 and GL-5 combo in that weight. Am I better off looking at just the GL-4 75w-90 gear oil?


ABSOLUTELY!

Your car would do fine with a 75w-80 fluid as well as long as it is a GL-4 fluid only. DO NOT USE A SYNCHROMESH fluid either many are only rated GL-3.

The Miata specifies GL-4 ONLY.... The difference between the specs is significant enough that even a compromise fluid that says GL-4+, GL-4/5, ect will not give the smooth shifting synchro performance that you want and that the OEM designed in. Stick with GL-4 ONLY plenty of fluids to choose from the only thing being you'll probably need to order from online unless you have a European/Japanese parts or performance shop nearby.

An alternative is a Japanese/European motorcycle shop or dealership....they will have dedicated GL-4 fluids more than likely.

Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385035 03/25/20 12:17 AM
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Molakule has a statement somewhere that you can't actually do both GL4/5...find a GL4.


If it's the truth....it can handle the pressure !!!
Re: GL-4/GL-5 gear oils a compromise? [Re: AC1DD] #5385037 03/25/20 12:27 AM
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Biggest prb with a higher than GL-4 rating is damage to the yellow metals synchro rings. And the GL-3 product doesn't protect against wear enuf. Just use GL-4. In spec'ing 75W-90 Mazda is trying to give it some better wear protection perhaps at a cost of some cold start-up shift smoothness. Try to find the lowest viscosity you can within this SAE grade. It's quite a range.


Mazda6 GX (i.e.Sport), 6MT, '17
Moto Guzzi 850 T5 (Euro version), '85
Honda Civic Si (EX 2 dr in the 'States), A/T, '97
Toyota Camry CE, 5MT, '99
Toyota Corolla VE, 4AT, '99
VW (Type2) Kombi, 4MT, '79
Re: GL-4/GL-5 gear oils a compromise? [Re: Cdn17Sport6MT] #5385040 03/25/20 12:41 AM
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Last edited by Cdn17Sport6MT; 03/25/20 12:42 AM.

Mazda6 GX (i.e.Sport), 6MT, '17
Moto Guzzi 850 T5 (Euro version), '85
Honda Civic Si (EX 2 dr in the 'States), A/T, '97
Toyota Camry CE, 5MT, '99
Toyota Corolla VE, 4AT, '99
VW (Type2) Kombi, 4MT, '79
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385050 03/25/20 02:54 AM
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Bailes1992 Online Content
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Ignore the API rating, find a specific manual tranmission oil with a viscosity to suit your usage and ambient conditions. Molakule has a list around here somewhere.


19 Volvo V40 D3 - Mobil1 ESP 5w30
19 Jeep Renegade eTorq - Castrol GTX 15w40
03 Ford Mondeo 3.0 V6 - Fuchs Titan Race Pro S 5W-40
96 LR Defender 300TDi - Motul 4100 15w50
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385059 03/25/20 04:59 AM
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2018 Lowered Hyundai Kona AWD 1.6T https://www.hyundaikonaforum.com/showcase/2018-kona-awd-1-6t-lowered.1162/
2014 Toyota Rav4 AWD
2005 Honda Civic
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385099 03/25/20 06:36 AM
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I personally don't like oils that are rated both GL-4 and GL-5, or rather don't trust them.
In manual transmissions with brass syncros, GL-4 is the only way to go.


1975 Ford Capri II Ghia 3000 V6 - 315k, Repsol Elite Super 20W-50
1988 Ford Escort XR3i Cabrio - 110k, Valvoline Maxlife 10W-40

Re: GL-4/GL-5 gear oils a compromise? [Re: FordCapriDriver] #5385106 03/25/20 06:52 AM
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4WD Online Confused
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Originally Posted by FordCapriDriver
I personally don't like oils that are rated both GL-4 and GL-5, or rather don't trust them.
In manual transmissions with brass syncros, GL-4 is the only way to go.


Reminds me of what we call a Fish & Ski boat … feels like a compromise happened
I know some GL5 print big & bold not for GL4 applications

Have used Redline in the transfer case but Delvac 1 in the pumpkins … it’s all good value then

Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385108 03/25/20 06:52 AM
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aquariuscsm Offline
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GL5 gear lubes also have additives that will make the gears crunch when you shift if used in a GL4 only spec tranny. GL4's have the proper add pack for shiftability.


1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Quaker State Ultimate Durability 10W30
2012 Honda Accord Coupe EX-L 2.4,auto,San Marino Red
Pennzoil Platinum High Mileage 10W30

Re: GL-4/GL-5 gear oils a compromise? [Re: aquariuscsm] #5385151 03/25/20 07:40 AM
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And seems many that are meant to take shocks are GL5 …
Being they have their own housings … and these products are sold in quarts or gallons … I’d be buying both if that’s what I needed … not like you service driveline kit that often anyway …

Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385192 03/25/20 08:28 AM
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From what I can work out, GL-5/GL-4 lubes are GL-5 lubes with selected additives that don't hurt brass components.

The lubes I don't understand are the likes of Fuchs Sintopoid 75w80 which is strictly an MTF but has API GL-5 rating, or even the Ford 'Honey' designed for MTX75 gearboxes.


19 Volvo V40 D3 - Mobil1 ESP 5w30
19 Jeep Renegade eTorq - Castrol GTX 15w40
03 Ford Mondeo 3.0 V6 - Fuchs Titan Race Pro S 5W-40
96 LR Defender 300TDi - Motul 4100 15w50
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385216 03/25/20 08:53 AM
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Bill_W Offline OP
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Is the target aftermarket 75w-90 GL-4 also need a balance of friction modifiers to closely match the OEM product or can I do better in aftermarket? OEM is pricy also... Some of the Mazda guys like the Motorcraft XT-M5-QS

Last edited by Bill_W; 03/25/20 09:01 AM.

Slick
Re: GL-4/GL-5 gear oils a compromise? [Re: Bill_W] #5385224 03/25/20 08:59 AM
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Just PM Molakule


'98 LEX LS400 310K
'02 4Runner 250K
'05 Lex LS430 90K
'07 Lex GX470 75K

Shell Gas and Truck 5w-30
Amsoil OE 10w-30
Toyota ATF's and Coolant
Amsoil Gear Oil and Grease
Re: GL-4/GL-5 gear oils a compromise? [Re: aquariuscsm] #5385228 03/25/20 09:03 AM
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Cdn17Sport6MT Offline
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Originally Posted by aquariuscsm
GL5 gear lubes also have additives that will make the gears crunch when you shift if used in a GL4 only spec tranny. GL4's have the proper add pack for shiftability.

++1


Mazda6 GX (i.e.Sport), 6MT, '17
Moto Guzzi 850 T5 (Euro version), '85
Honda Civic Si (EX 2 dr in the 'States), A/T, '97
Toyota Camry CE, 5MT, '99
Toyota Corolla VE, 4AT, '99
VW (Type2) Kombi, 4MT, '79
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