ND Miata Manual Transmission and Differential Fluids for Track Use

[randomhero439]

Hello - I am approaching the start of the 2026 HPDE season with my new MX-5 Miata. The car will see about 9-12 track days this year. I'm an instructor/advanced driver so the car will get pushed pretty hard. It's a 2025, and right now has about 600 miles on it. I'd like to get around 1,200 miles on it and do an engine oil/filter and driveline fluid change to get majority of the break-in material and silicone out of the fluids. Similar approach to BMW ///M cars, Mercedes AMG and C7 Corvettes.

I'm set on the engine oil and filter, but I am researching different driveline fluids. OEM from Mazda is 75w-90 GL-4 2.0L (2.1qt) in the transmission, and 75w-85 GL-4 0.6L (0.6qt) in the diff. These fluids are about $243 shipped.

I've looked into the Redline fluids and Amsoil fluids. Both sets can be had for about $110 shipped, and likely more suitable for track work than the OEM fluids while still maintaining the factory warranty. Driveline oil change interval is planned to be once per year, at the end of the season.

Amsoil 75w-90 GL-4 MTG
Amsoil 75w-85 GL-5 SVL
Redline MT-90 75w-90 GL-4
Redline 75w-85 GL-5

I like that the Amsoil comes in the easy squeeze packs.

What else should I be considering when deciding on a driveline fluid for track use, while maintaining the OEM specs?

 

[wwillson]

What is "ND"?

 

[gogydm]

Latest generation, 2016 - Present.

 

[dnewton3]

What else should I be considering when deciding on a driveline fluid for track use, while maintaining the OEM specs?

Nothing wrong at all with Amsoil and RedLine, but since you asked, perhaps also look into HPL.

When it's time to purchase, if you choose Amsoil, please consider using our site sponsor, Pablo. If HPL, they will occasionally have BITOG specific discount sales days; check them out.

 

[RallyXaDSM]

I would personally go no thinner than 75w90 in the diff for track use. Seems that specialists like Flyin' Miata agree. If you must stick to the OEM weight (would they even warranty a diff if it gets destroyed by track use?) then the Amsoil 75w85 is closer to a 90 than the Redline is and would be my choice.

 

[martinq]

I would personally go no thinner than 75w90 in the diff for track use. Seems that specialists like Flyin' Miata agree. If you must stick to the OEM weight (would they even warranty a diff if it gets destroyed by track use?) then the Amsoil 75w85 is closer to a 90 than the Redline is and would be my choice.

Strongly agree. Unless you're just toodling around I would expect to see significant heat in your differential and transmission fluids while on track. Are there temperature sensors in there to monitor?

 

[randomhero439]

Strongly agree. Unless you're just toodling around I would expect to see significant heat in your differential and transmission fluids while on track. Are there temperature sensors in there to monitor?

Yeah, I expect things to get pretty hot. The car is mostly stock, brake upgrades, no power adders, and the wheels are stock with 200TW tires. Nothing too serious.
The 85 should help a with the heat.

 

[IndyIan]

Yeah, I expect things to get pretty hot. The car is mostly stock, brake upgrades, no power adders, and the wheels are stock with 200TW tires. Nothing too serious.
The 85 should help a with the heat.

I don't think you'll be overheating the transmission or diff, on a track. Probably the highest average hp over a lap is like 80hp? So the diff and transmission only need to dissipate 5-6 hp in heat? And say averaging 70mph, there is a bit of airflow for them? I would doubt they get over 200f unless their is a undertray that restricts air flow?
Still put good fluid in them and change it more often, but I would take a heat gun reading after a session and see. Probably the engine oil is a bigger concern with all the high rpm running it will see.

 

[martinq]

Yeah, I expect things to get pretty hot. The car is mostly stock, brake upgrades, no power adders, and the wheels are stock with 200TW tires. Nothing too serious.
The 85 should help a with the heat.

85?
I don't follow.

 

[randomhero439]

I don't think you'll be overheating the transmission or diff, on a track. Probably the highest average hp over a lap is like 80hp? So the diff and transmission only need to dissipate 5-6 hp in heat? And say averaging 70mph, there is a bit of airflow for them? I would doubt they get over 200f unless their is a undertray that restricts air flow?
Still put good fluid in them and change it more often, but I would take a heat gun reading after a session and see. Probably the engine oil is a bigger concern with all the high rpm running it will see.

Good idea with the heat gun. I think it will be well over 200F though. Yeah, I’ve heard they run hot on the engine oil. I landed on Mobil 1 Extended Performance 0w20 and a genuine Mazda filter. It’s the best oil I can find that meets the API/ILSAC requirement. The genuine filter should keep the flow as designed, and not increase restriction like a higher efficiency filter could be.

85?
I don't follow.

75w-85 instead of 75w-90. Improved efficiency and flow will help reduce heat.

 

[martinq]

Good idea with the heat gun. I think it will be well over 200F though. Yeah, I’ve heard they run hot on the engine oil. I landed on Mobil 1 Extended Performance 0w20 and a genuine Mazda filter. It’s the best oil I can find that meets the API/ILSAC requirement. The genuine filter should keep the flow as designed, and not increase restriction like a higher efficiency filter could be.


75w-85 instead of 75w-90. Improved efficiency and flow will help reduce heat.

You will trade less heat for higher wear I think?

Regardless I would check / clean your magnets after each event to see how it's going. Get magnetic drain & fill plugs if they're not already installed.

 

[Oliveoil2]

I’ve had very good luck with Redline transmission and diff fluids. The MT 90 in the 5 speed and transmission and the 75w-90 for the rear diff. But you can’t go wrong with any of the recommendations.

 

[randomhero439]

Ended up ordering Amsoil through Pablo. I'm looking forward to trying the easy squeeze pouches, a big selling point for me. I also added a few bottles of P.i. fuel additive for the Audi and BMW to get free shipping It's been awhile since they've gotten a fuel treatment beyond normal top tier fuel use.

 

[dedonderosa]

id go amsoil 75w110 in the rear end

 

[xspeedy]

What is "ND"?

And within the ND range, there are three sub generations (two facelifts or LCIs). ND1, ND2, ND3.

 

[xspeedy]

For the OP, what do the Spec Miata folks run?

 

[randomhero439]

For the OP, what do the Spec Miata folks run?

Miata Global Cup runs 75w-90 in the transmission and differential, and 5w-40 in the engine with a Mazda OEM filter. The brands are whomever is the sponsor. In the past it was Castrol, Idemitsu, and this year I think it’s Motul. Using 300V for the engine.

The diff is a Drexler unit with an external cooler and filter. The transmission is a sequential unit.

 

[martinq]

Miata Global Cup runs 75w-90 in the transmission and differential, and 5w-40 in the engine with a Mazda OEM filter. The brands are whomever is the sponsor. In the past it was Castrol, Idemitsu, and this year I think it’s Motul. Using 300V for the engine.

The diff is a Drexler unit with an external cooler and filter. The transmission is a sequential unit.

If you're looking to pick up a few HP then go with thinner fluid like 70w80 or 75w85 (same for engine, 0w12, 0w16, etc) and change after each session. If you're trying to protect, then go heavier (75w90/110) and monitor temperatures.

 

[Dutchy491]

Ended up ordering Amsoil through Pablo. I'm looking forward to trying the easy squeeze pouches, a big selling point for me. I also added a few bottles of P.i. fuel additive for the Audi and BMW to get free shipping It's been awhile since they've gotten a fuel treatment beyond normal top tier fuel use.

Cool….but which gear lube?

 

[randomhero439]

Cool….but which gear lube?

Transmission 75w-90 GL-4
Differential 75w-85 GL-5