JASO T903 and T904: What Motorcycle Oil Standards Actually Mean (2023 Update)
JASO T903 and T904: The Real Deal on Motorcycle Oil Standards (2023 Edition)
If your bike runs a wet clutch, your oil isn't just for the engine — it's pulling triple duty:
Lubricating the engine
Cooling and protecting the transmission
Keeping your clutch from slipping under load
That's why you need more than just“synthetic”on the label. You need oil that's been tested and approved to the JASO standards — especially now that they've been updated for today's bikes.
What Is JASO T903?
JASO (Japanese Automotive Standards Organization) created the T903 spec specifically for 4-stroke motorcycles. It’s one of the only oil standards that actually tests how oil performs on:
Wet clutch engagement
Gearbox shear
Friction stability
Emissions compatibility (2023+)
Most automotive oils? They don't care about any of that. They're built for cars — not for your bike's shared sump and screaming RPMs.
🧠 Tech Talk: T903 handles overall engine oil performance. T904 is the embedded test for clutch friction (we'll get to that below).
MA, MA1, MA2, MB — What They Mean
Grade | Clutch Type | Friction Level | Use Case |
---|---|---|---|
MA | Wet clutch | Moderate | Standard spec, safe for most bikes |
MA1 | Wet clutch | Lower | Older bikes or smoother feel |
MA2 | Wet clutch | Higher | Sport, aggressive riding, towing |
MB | NO wet clutch | Very Low | For scooters/CVT only – 🚫 NOT safe for wet clutches |
🛠️ Mechanic Talk: If your clutch runs in oil (wet clutch), MB is a no-go. Use MA or MA2. MA2 gives you extra bite — especially under torque or heavy load.
If you're wondering about the difference between MA vs MA2 oil, it comes down to friction performance and clutch feel.
Choosing the right wet clutch oil rating helps avoid slippage under load.
What's New in JASO T903:2023?
As of May 2023, the spec was revised to meet modern motorcycle demands — cleaner emissions, hotter engines, tighter tolerances.
Key Changes:
Phosphorus max lowered to 0.10%
🧪 Reduces catalyst poisoning, especially for bikes with emissions systems.
Evaporation (Noack) limit dropped to 15%
🔥 Means less oil burn-off and more consistent performance.
Outdated API specs removed
🚫 SG and SH are gone. Now requires at least API SJ — with SN Plus or SP preferred.
Updated friction test
🛠 Uses new reference oil (JAFRE-B23) and clutch plate material to reflect modern bikes.
🗓 These changes took effect for licensing on October 1, 2023.
What is JASO T904 and Why It Matters
T904 is the wet clutch friction test, now officially part of T903 as Annex A.
It uses a friction rig (like the SAE #2) to simulate real clutch behavior, measuring:
DFI (Dynamic Friction Index) – Acceleration grip
SFI (Static Friction Index) – How well the clutch holds at idle
STI (Stop Time Index) – How cleanly it disengages on shifts
These friction numbers are what separate MA1 from MA2. It's not marketing — it's machine-verified data.
Why Car Oil Can Kill Your Clutch
Automotive oils often use friction modifiers to improve MPG. That's great for sedans. But on a motorcycle?
It can glaze your clutch plates
Cause slippage under load
Lead to clutch fade or chattering
And destroy your transmission's synchros over time
🧼 Bottom line: If it's not JASO-rated, don't run it.
Picking the Right Oil
Riding Style | JASO Grade | Why It Works |
---|---|---|
Commuter / All-around | MA or MA1 | Balanced grip and smoothness |
Sport / Track / Aggressive | MA2 | Higher friction, better clutch lockup |
Touring / 2-up / Loaded | MA2 | Grabs better under weight and heat |
Scooter / CVT | MB | No clutch to worry about |
How to Read the Label
Final Word
Whether you wrench for a living or just love your bike, knowing the difference between MA, MA1, MA2, and MB can save you a clutch job — and a headache.
👉 Shop JASO MA2-Safe Motorcycle Oils
✅ Wet clutch approved
✅ Meets or exceeds T903:2023
✅ Lab tested — rider trusted
FAQs About JASO Certification
JASO MA is a Japanese motorcycle oil standard that ensures proper wet clutch performance and engine protection.
MA2 offers improved friction performance over MA, making it ideal for performance bikes and sport riding.
Yes. JASO MA2 oils are designed to be compatible with modern emissions systems and will not harm catalytic converters.
Check the back label for the official JASO box marked with MA or MA2. If it’s not labeled, it’s not certified.
Yes. JASO MA2 exceeds the performance specs of MA and is fully backward-compatible.
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