Which oil for a motorcycle or scooter: JASO MA2 or MB?

It is time to change your motorcycle’s oil, and in the garage there is an almost full can left over from the car. It is engine oil, the engine runs on petrol — why not? Sound familiar? This site is about car oils, but motorcyclists buy their oil from the same shelves, and leftover “energy-saving” car oil is their most common mistake. That is exactly what a separate Japanese standard for motorcycle oils, JASO T 903, protects against.

One oil for the engine, gearbox and clutch

In a car with a manual gearbox every unit has its own oil, and the clutch is dry. Most motorcycles are different: one and the same oil lubricates the engine, the gearbox and the clutch, which runs in an oil bath (a “wet” clutch). In other words, a motorcycle’s engine oil is gear oil as well.

Car oils, meanwhile, have long been heading the other way: to save fuel they are getting thinner, and friction modifiers are added to them. In the engine that is a plus, but in a wet clutch it goes like this: friction modifiers => the plates grip less well => the clutch slips under load. Brake pads rubbed with floor polish would behave in much the same way.

The second problem is the gears in the gearbox: such an oil can cause pitting (flaking of the tooth surface), and the gears themselves grind the oil down, so its viscosity drops. Nor are these theoretical horror stories: the JASO developers write that problems have already occurred in service, most probably for exactly this reason.

What MA, MA2, MA1 and MB mean

JASO T 903 is the Japanese standard for oils for four-stroke petrol motorcycle engines. It was issued in March 1998 with the MA and MB classes, and in 2006 the MA class was split into MA1 and MA2. These classes have already been covered briefly in the article on engine oil quality classifications.

The class is determined on a test rig with clutch plates by three measures: dynamic friction, static friction and stopping time. MB is a reduced-friction oil, MA a high-friction one. The upper, “grippiest” part of the MA range is MA2, the lower part is MA1, so any MA2 oil is also an MA oil.

Wet clutch: MA and MA2

Most motorcycles call for MA. Honda, for example, writes in its current European owner’s manuals (from the CBR600RR to the Africa Twin): JASO T 903 MA, SAE 10W-30, API SJ or higher. Suzuki, in its JASO information sheet, puts it even more simply: its motorcycles and ATVs need MA, and not one of them needs MB.

On the shelves you will mostly see MA2: most of the oils in the JASO register are MA2, while MA1 is hardly ever seen. But an MB oil must not go into an engine designed for MA: the clutch may slip.

Scooter with a CVT: MB

MB is for scooters with a belt CVT and a dry centrifugal clutch: their clutch never sees the engine oil, so the reduced friction has nothing to spoil there. But MB only where the manufacturer explicitly requires it: for some scooters MA is specified too. And the rear-wheel final drive in many scooters has a separate oil with its own schedule — check the owner’s manual.

What the JASO T 903:2023 edition changed

For a motorcycle owner, three changes in the current 2023 edition matter.

1. API class no lower than SJ. A JASO oil must also meet an API class. The 2016 edition allowed API from SG upwards, as well as ILSAC and ACEA; the new one kept only SJ, SL, SM and SN, added SN PLUS and SP, and in every case excluded the “energy-saving” Energy Conserving and Resource Conserving versions.

2. Less phosphorus: 0.08-0.10% by mass instead of 0.08-0.12%. The upper limit was lowered to protect the catalytic converter, the lower one was kept for protection against wear and pitting.

3. Less evaporation: no more than 15% instead of 20%, meaning lower oil consumption and more stable viscosity.

What the standard still does not have, though, is the long-awaited separate gear pitting test.

The “JASO T903:2023” mark has been allowed since 1 October 2023, and oils registered under the old edition may carry the “T903:2016” wording until 30 April 2028. So both markings on the shelf are normal, not a sign of a counterfeit.

How to read the can: JASO, API and viscosity

The most important thing on the can is the JASO box: the oil code, the class, the edition of the standard and a line saying that conformity is guaranteed by the named company. JASO does not test or approve oils: the supplier tests the oil itself, submits the data to the JASO committee (its secretariat is the Japan Lubricating Oil Society, JALOS) and declares the class on its own responsibility, while the committee only issues the code and spot-checks oils from the market. So “JASO approved” on a can is a reason to be on your guard.

The code, on the other hand, can be checked: JALOS keeps an open register of motorcycle oils in English (the list itself is a PDF at the bottom of the page). If you cannot find your code, or the class there is different, take a closer look at the seller (for other ways to check, see the article how not to buy counterfeit oil).

The API “doughnut” on a motorcycle oil speaks only for its “engine” part: API, ILSAC and ACEA write requirements for cars, not for clutches. If the “doughnut” says Resource Conserving (on older cans, Energy Conserving), the oil is not suitable for a motorcycle with a wet clutch: such oils are ruled out both by Honda’s manuals and by JASO T 903 itself. The same goes for the ILSAC “starburst”, the mark of the same fuel economy. What these marks mean is explained in the article on API SQ and ILSAC GF-7.

And a 10W-40 car oil without the “energy-saving” marks? Nobody knows how it will behave in the clutch: it has never been through the clutch-plate test.

Viscosity is whatever the manufacturer has specified: 10W-30 for Honda, 10W-40 for Suzuki (what these figures mean is in the article how to decode the viscosity index). JASO itself does not prescribe a viscosity grade; it only sets a floor: the oil must not be too thin in a hot engine or lose too much viscosity under the gears.

What about two-stroke engines?

For two-stroke engines (motorcycles, snowmobiles, chainsaws) both the oil and the standard are different: JASO M 345. Here the oil burns together with the fuel, so there are three classes, told apart mainly by smoke and cleanliness: FB, FC (less smoke and fewer exhaust deposits) and FD (like FC, but cleans better at high temperatures); the former FA is gone. And the equals sign between FD and EGD under the international standard ISO 13738 is only a common simplification: look for the class the manufacturer has specified.

When to change it, and what does it mean for a motorcycle owner?

There is no single answer: even one Honda manual gives two schedules, for different markets. As a rule, the first change is made after running-in, then according to the manual, and more often if you ride in rain and dust. And do not pour the drained oil out just anywhere — where to take it is covered separately.

I will say it once more: which oil to use is decided by the manufacturer, and for a motorcycle this rule works just as it does for a car (more in the article on how to find out the manufacturer’s recommendations). Find the JASO class, the viscosity and the API class in the owner’s manual, and look for exactly those on the can, not for “for motorcycles” in big letters. Is your manual older than JASO, naming only an API class? For a wet clutch, take an oil of that class with a JASO MA or MA2 box. A dry clutch and a separate gearbox oil, as in a car, are another matter: that is how it is done, for example, on the Kyiv-built Dnipro. And the leftover car oil is better saved for the car: it is no gift to a motorcycle.