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JASO Standard

The JASO Engine Oil Standards Implementation Panel was established by industrial and academic associations related with engine oil products in Japan, for the purpose of establishing JASO Engine Oil Standards in domestic and overseas markets. It was decided that the different design characteristics of Japanese-manufactured engines required a higher standard of specification than the commonly used API (American Petroleum Institute) Standards.


Engine oils subject to the Automotive Diesel Engine Oil Standard JASO M 355: 2008 shall be classified into DH-1, DH-2 and DL-1, all of which apply to four-cycle diesel engines.

DH-1 classification has been developed for the diesel engines which are subjected to long-term exhaust emission regulations, and stipulate requirements for performance in such conditions as wear prevention, corrosion prevention, high-temperature oxidation stability, and soot control. Further, oils conforming to DH-1 standard (hereinafter “DH-1 Oils”) are intended for suppressing deterioration of piston detergency, formation of deposits at high temperature, foaming, oil consumption due to evaporative loss, viscosity decrease by shear, deterioration of oil seals, etc. The DH-1 Oils are also applicable to engines which were predating the long-term exhaust emission regulations. Based on the premise that the drain intervals recommendation specified by engine manufacturers are observed, application of a DH-1 Oil is also allowed to cases where diesel fuel having more than 0.05% sulfur content is used.

DH-2 and DL-1 classifications have been developed for the engines which are equipped with after-treatment devices such as Diesel Particulate Filter (DPF) and catalyst in compliance with exhaust emission regulations subsequent to the new short-term regulations. Oils conforming to these standards (hereinafter “DH-2 Oils,” “DL-1 Oils”) have an excellent applicability to DPF and catalyst while keeping the same performance level as required for DH-1 classification. Note that because required levels of engine oil are different between for truck/bus and for passenger car class in engine durability, oil change distance, fuel economy, etc., DH-2 classification is adopted for heavy-duty use by trucks/buses and DL-1 classification is adopted for light-duty use by passenger car classes.

DH-2 Oils and DL-1 Oils can be used only in the environment where low-sulfur diesel fuel having not more than 0.005% sulfur content is used.

Based on the premises that low-sulfur diesel fuel having not more than 0.005% sulfur content is used and that the user complies with oil change distance recommended by the engine manufacturer, application of a DH-2 Oil is also allowed to engines predating the new short-term exhaust emission regulations.

2T specifications

Japenese motorcycle manufacturers found the limits demanded by the API TC specifications too loose. Oils meeting the API TC standard still produced excessive smoke and could not prevent exhaust blocking. Therefore the Japanese Engine Oil Standards Implementation Panel (JASO) introduced the following specifications:

JASO FA
Original spec established regulating lubricity, detergency, initial torque, exhaust smoke and exhaust system blocking.
JASO FB
Increased lubricity, detergency, exhaust smoke and exhaust system blocking requirements over FA.
JASO FC
Lubricity and initial torque requirements same as FB, however far higher detergency, exhaust smoke and exhaust system blocking requirements over FB.
JASO FD
Same as FC with far higher detergency requirement.

During the mid-90s it became clear that the JASO Specifications could not satisfy the requirements of the modern European two-stroke engines. The ISO standards listed below were developed to address this shortcoming. Their basis is the relevant JASO standard + they require an additional 3h Honda test to be run to quantify piston cleanliness and detergent effect.

ISO-L-EGB
Same requirements as JASO FB + test for piston cleanliness.
ISO-L-EGC
Same requirements as JASO FC + test for piston cleanliness.
ISO-L-EGD
Same requirements as JASO FD + test for piston cleanliness + detergent effect.

4T specifications

Modern passenger car engine oils contain more and more friction modifiers. While this is the good thing for those segments (reduces wear and fuel consumption) it's bad for the motorcycles. At least for those motorcycles which use engine oil to lubricate their transmission and wet clutch. JASO introduced the MA and MB specification to distinguish between friction modified and non friction modified engine oils. Most four-stroke motorcycles with wet clutches need a JASO MA oil.

JASO MA
Japanese standard for special oil which can be used in 4-stroke motorcycle engine with one oil system for engine, gearbox and wet clutch system. Fluid is non-friction modified.
JASO MB
MB grade oils are classified as the lowest friction oils among motorcycle four-cycle oils. Not to be used where a JASO MA grade oil is required.


Last modified on Tuesday, 12 May 2015 12:42

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