What JASO M345:2024 Actually Tests in a Two-Stroke Oil: The Four Test Methods Behind FB, FC and FD

Last verified: 2026-07-28

No — a JASO FD oil is not required to be any more lubricating than a JASO FB oil. JASO M345:2024 does not run one test on "the oil"; it grades a formulation across four separate JSAE engine-bench procedures — JASO M340 (lubricity), M341 (detergency), M342 (smoke) and M343 (exhaust-system blocking) — and FB, FC and FD are three different pass bars set on those same four tests, not four different tests. Move from FB up to FD and one of those four bars never moves at all; step from FC to FD and only one of them does.

JASO M345:2024 sets minimum performance indices on four separate engine-bench procedures — lubricity (M340), detergency (M341), exhaust smoke (M342) and exhaust-system blocking (M343). FB, FC and FD share the identical lubricity minimum; detergency rises at every step; smoke and blocking rise only from FB to FC, then hold flat all the way to FD.

A JASO letter grade on a quotation, TDS or label is a specific and limited claim, and most of what it leaves out is invisible on the label itself. Our motorcycle oils coverage introduces the grades themselves.

What does a JASO grade actually measure?

JASO M345 sits on top of four independent bench-test procedures, developed by the 2-Cycle Oil Subcommittee inside JSAE's Motorcycle Committee. Each one has its own standard number and evaluates one thing:

• JASO M340 — the lubricity test procedure, which also returns a second index, initial torque, from the same bench run.
• JASO M341 — the detergency test procedure, scored on two separate parts: the fundamental part and the piston-skirt part.
• JASO M342 — the smoke test procedure, measuring exhaust smoke formation.
• JASO M343 — the exhaust-system blocking test procedure.

M345 is the classification layer. It takes the four numbers each formulation produces on M340–M343 and translates them into one of three labels. That is the whole mechanism: four tests in, one letter out. The letter tells you which minimum bar the formulation cleared — never what it scored beyond that bar.

Why is FD not simply "better" than FB?

Here is the table that makes the point better than a paragraph could. It reproduces the standard indices JASO's own manual sets for each grade, evaluation item by evaluation item.

Source: JALOS, JASO M345:2024 Implementation Manual (May 2025), Table 2 — "JASO Test Procedures and Standard Indices." The column is captioned "Standard Index (min.)" in the manual itself: these are performance indices, not physical units.

Read across a row and the shape tells its own story. Lubricity: 103, 103, 103 — the standard asks no more of an FD oil's film strength than of an FB oil's. Initial torque: 98, 98, 98 — same story. Detergency is where the grades actually separate, rising at every step on both sub-tests. Smoke and blocking rise once, from FB to FC, then hold flat into FD.

Both detergency parts come from a single 180-minute run of M341, and that run is the same length for all three grades. What changes between FB, FC and FD is the score the oil has to reach, not the time it spends being tested.

The manual's own words say it more plainly than the table does. FC "is defined for low smoke 2-cycle oils superior to FB with regard to exhaust smoke and exhaust system blocking." FD "is defined as improved version of FC in terms of detergency performance at high temperatures." Read FC and FD for what they claim to add — not for a blanket "better" across every property the standard touches.

Against an FC oil, FD does not mean cleaner-burning, and it does not mean more film strength. It means one thing: better detergency at high piston-skirt temperature.

Why do the 2018 and 2024 smoke-test numbers disagree?

This standard has now been revised twice in a row for equipment reasons, not performance reasons — and that is the piece most readers of the index table miss. The first revision, finalized in March 2018, happened because the engine used for JASO's bench tests "encountered production cancellation, which made the continuation of test difficult"; the standard was revised "to accommodate the new test engine so that the standard can be utilized at length." The second revision, reflected in the M342-2024 row above, happened "in order to correspond to the termination of manufacture and maintenance of the testing apparatus for exhaust smoke of JASO M342." Same category of cause, different piece of hardware.

That is why Table 2 lists two smoke rows side by side rather than one: 45/85/85 under the 2018 apparatus, 40/80/80 under the 2024 apparatus. An index is a score measured on a specific rig — change the rig, and even an unchanged oil can return a different number. The manual lists both rows without stating a cutover date and without saying one retires the other. Reading the 2024 figures as "40 instead of 45, so the bar dropped" mistakes the ruler for the requirement.

So when a document lists "JASO M342-2024," read it as "measured on the current apparatus." Don't read it as a tougher — or looser — bar than the 2018 figure. On this evidence, an edition year on a two-stroke oil spec is not a quality milestone. It's confirmation the lab equipment behind the number still exists.

Who actually stands behind a JASO FB/FC/FD claim?

This is the section worth reading slowest, because it is where "JASO FD certified" earns air quotes. JASO's own manual states, in Section 5 on labeling, that a submitter "shall expressly state that the Submitter makes such performance classification and labeling on his/her own responsibility." The same section instructs that a user of the standards "shall not use in advertising a description which might lead to the misunderstanding that the Panel approved or certified the quality and performance of the 2-cycle oil concerned."

Read that twice. "JASO FD certified" or "JASO FD approved" sits close to the exact wording the issuing panel tells submitters not to use.

What actually happens on file is narrower than "certification." The submitter warrants, in the notification documents themselves, that the reported results "indicate typical figures of the 2-cycle oil concerned, and represent performance of the product that will be marketed" — and separately confirms that "the retained tests reports are kept under our own responsibility." The Panel holds the filing: the oil code, the grade, the submitter's name. The submitter holds the underlying test reports. There is a backstop — the Panel "may take arbitrary samples of JASO engine oil category FB, FC or FD from the market" and check the performance marking and quality against the on-file documents — but that check runs after the product is already on shelves, not before.

One more currency check costs nothing: search the current manual for the letter combination "FA," the grade JASO used before FD was introduced. It returns zero results. FA is gone. A supplier still quoting "JASO FA" on a 2026 document either hasn't refreshed their paperwork in a long while, or is naming a grade the current standard does not recognize. Either way, it's worth asking why.

Does "meets ISO 13738" mean the same thing as JASO FD?

Treat this one with more caution than the rest. JASO's own manual documents a real, close relationship with ISO at the method level: ISO 6743-15, the lubricant-family classification standard, "was established in March 2000 adding the detergency test with longer duration," and "in order to correspond this, JASO standard was revised in fiscal 2002." That is a documented, on-the-record coordination between the two bodies' test methods.

What the manual does not document is a letter-for-letter equivalence table between JASO's FB/FC/FD and ISO's own two-stroke performance levels under ISO 13738 — currently the 2011, second edition, which cancelled the 2000 edition and was reconfirmed by ISO in 2022. Two claims circulate about that relationship: that ISO-L-EGD and JASO FD are simply the same grade under two names, and, separately, that the ISO grades are strictly stricter because they add a piston-cleanliness requirement JASO does not test. Neither claim traces back to the standards' own published text in what we can verify here.

Related is not identical. Don't accept either claim on a supplier's say-so. If a document pairs an ISO two-stroke designation with a JASO grade, ask for the specific ISO designation, in writing — not an unqualified "equivalent to JASO FD."

Does JASO M345 set the fuel-to-oil mixing ratio?

No, and this is worth stating flatly because the conflation is common. A direct search of the current implementation manual for any mixing-ratio term — 50:1, 40:1, 32:1, any ratio at all — returns zero results. JASO M345 grades the quality of the oil across the four test procedures above. It says nothing about how much of that oil to mix with the fuel.

The mixing ratio comes from the engine manufacturer, not from the oil's classification, and two engines that both call for a JASO FD oil can specify two different ratios. A technical sheet that states "JASO FD, 50:1" in one line is citing two facts from two different authorities. Verify each one against its own source — never treat the ratio as something the JASO grade implies.

Is a JASO filing valid for an outboard motor?

Not automatically. JASO M345 covers two-stroke gasoline engines broadly, and the manual's own foreword names outboard motors, alongside motorcycles and utility equipment, among the two-stroke engine types Japan produces in volume. But marine two-stroke oils typically run on a separate performance track: NMMA TC-W3, administered by the U.S. National Marine Manufacturers Association, not by JASO's panel.

A JASO M345 filing and an NMMA TC-W3 registration are independent programs, run by different bodies, and holding one does not mean a supplier also holds the other. For an outboard or marine two-stroke sourcing decision, ask which of the two — or both — the product is actually registered under. Our outboard engine oil coverage sets out what a genuine TC-W3 claim needs to show.

How do you verify a JASO grade before you accept it?

Four checks close most of the gap between what a document claims and what the standard actually requires.

First, read the grade for what it adds — detergency stepping up FB to FC to FD, smoke and blocking stepping up only as far as FC — never as a blanket "better" on lubricity or anything else the index table holds flat. Second, treat an edition-year figure on the smoke test as an apparatus reference, not a performance upgrade, unless the supplier can show otherwise in writing. Third, ask for the oil code reference number the filing was recorded under; JASO's market-survey mechanism checks samples against that record, but it runs after the fact, not as a pre-shipment certificate. Fourth, wherever an ISO or NMMA equivalence is claimed alongside the JASO grade, request the specific designation in writing rather than accepting the word "equivalent" on its own.

None of this requires taking a supplier's word alone, or the standard's silence, as the last word. When you send a request for quote on a two-stroke oil, ask the supplier to state the exact JASO grade, the M345 edition reference on the test used, and the oil code — in the document itself, not in a follow-up message. That's a small ask, and it's the difference between a claim you can check and one you can't. For how oil, part and packaging claims get verified across other standards families, see our lubricant certifications and approvals guide.

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