Motorcycle Oil Information

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Motorcycle oils can be divided into 2 basic categories, oils for 2 stroke engines & oils for 4 stroke engines. If you don't know the difference between the 2 engine types, click on the link below for a simple explanation.
The Basic Differences Between 2 & 4 Stroke Motorcycle Engine's

What the Numbers & Letters Mean

SAE (Society of Automotive Engineers) Grades

10w = This is a grade for the weight (or thickness) of the oil at colder ('winter') temperatures. To get this grade, the weight of the oil is tested at 0°F

40 = This is a grade for the weight (or thickness) of the oil at hotter temperatures. To get this grade, the weight of the oil is tested at 200°F

Number	10w	40
Meaning	Defines the viscosity (thickness) of the oil at it's coldest operating temperatures. This first number is used to show the viscosity of the oil used in an engine during winter when starting the vehicle from cold. The 'w' stands for 'winter'. Different countries often require different grades of oil, depending on how warm or cold the winters are. e.g. 10w40 is often used in the U.K, where as a country that has harsher or colder winters might use a 20w40. The oil viscosity or weight for cold temperatures is tested at 0°F. Generally speaking, the higher the number, the thicker the oil	This is the number or grade that defines the oils viscosity or thickness at higher operating temperatures. The oil viscosity or weight for hot temperatures is tested at 200°F.

API (American Petroleum Institute) Grades

A Double letter 'API' code classifies oils as suitable for different uses. The first letter of the API grade shows the type of engine an oil can be used in (either petrol or diesel). All petrol engines are classified 'S' which stands for 'spark ignition engines'. All diesel engines are classified 'C' which stands for 'compression ignition engines'.
The second letter of the API grade defines the quality of the oil. Ratings start with the letter 'A' (which is the lowest quality) & currently go up to the letter 'J' (which is currently the highest quality).

JASO (Japanese Automotive Standards Organization)

JASO 2 Stroke Oils: In 1994, the Japanese Automotive Standards Organization (JASO), developed a set of standards for 2 stroke oils. The standards were assigned according to a 2 stroke oils lubrication properties, detergents, initial torque (acceleration), exhaust smoke formation & exhaust system blocking (as 2 stroke oil burns, oil is deposited in the exhaust system, exhaust system blocking measures how much oil is deposited).
There are 3 classification grades for 2 stroke oils FA, FB & FC. The grade JASO FA is the lowest grade, assigned to oils which provide minimum performance characteristics & FC is the highest grade.

JASO 4 Stroke Oils: In 1998, the Japanese Automotive Standards Organization (JASO), developed a set of standards for 4 stroke oils which were measured against an oils ability to resist clutch friction & slippage & to prevent wear & pitting in the gear box.
There are 2 classification grades for 4 stroke oils Ma & MB. The grade JASO MB is lower a friction oil & MA is relatively higher friction oil.

The Difference Between Mono-Grade & Multi-Grade Oils

Single or Mono Grade Oil = (e.g. SAE 15w) This is an oil which is only suitable for use within a very narrow temperature range. SAE monograde oils usually fall into 2 main categories. The grades with a 'w' after them (SAE 5w, 10w, 15w & 20w) are only suitable for use in winter time because they are generally thin oils which are good for use in winter or for cold starting. The 'summer time' grades (SAE 20, 30, 40 & 50) are more suited for warmer (or summer time) temperatures or for use in an already hot engine.
The problem with single grade (or mono grade) oils is that they can only operate efficiently over a small temperature range. For example, a SAE 10w oil is fairly thin which is good for cold starting but it becomes to thin for effective lubrication as the temperatures rise (as the oil gets hotter, it starts to lose it's viscosity or thickness). A SAE 40 oil is fairly thick, which provides good lubrication when the engine is hot, but thick oils can cause drag when used from cold (e.g. starting the motorcycle first thing in the morning)
Gear & gear box oils, which are used in engines where the gearbox is separate from the engine, are mono grade oils but they use a different range of SAE grades to measure their viscosity. The commonest grades for gear oils are SAE 80 & SAE 90. As a very rough guide, SAE 90 gear oil has the same viscosity as SAE 50 engine oil
Gear oils used for certain applications (e.g. certain racing applications) are prefixed by the letters 'EP' which stands for extreme pressure

Multi Grade Oil = (e.g. 10w40) In the 1960's, long chain polymers started to be used in engine oils to improve the oils viscosity index's (basically meaning the oils were effective over a much wider temperature range). This led to the creation of multi grade engine oils (like 10w40 or 15w20), which is the type of engine oil used by most modern motorcycles.The most widely used multi grade oil is 10w40, which operates as a thin 10w weight oil at 0°F & as a 40 weight oil at 200°F

Different Types of Motorcycle Oils

Animal & Vegetable oils: Animal oils & fats used to be used for greasing horse & cart axles, but animal fats are not suitable for motorcycle engines as they oxidise (burn) at low temperatures & will form a clogging gum or varnish. Most vegetable oils have the same drawbacks as animal fats, except castor oil.
Castor oil has very good lubrication properties when under heavy load. Unfortunately, castor oil still oxidises very easily, which often means motorcycle engines running on castor oil need frequent engine strips to remove deposits. Castor oil was widely used in racing applications many years ago, & is still sometimes used today.

Mineral oils: Mineral oils are made by the fractional distillation of crude oil, which is the same method used to extract petrol from crude oil.
Mineral oils are able to withstand higher temperatures & are much less prone to oxidation which makes them much more suited to conditions inside an engine.

Synthetic oils: Synthetic oils are chemically manufactured. Although they are generally more expensive, synthetic motorcycle oils don't suffer from oxidation & have extremely high lubrication qualities which makes them ideal for high power, high speed engines.

Semi-Synthetic oils: Semi-synthetic oils are used in motorcycle engines as a good compromise between performance & expense as many motorcycle engines don't require a fully synthetic oil to operate. A semi synthetic oil is an oil that is supplemented with additives which prolong the oil service life and reduce the wear to acceptable level.

Oil Additives

Oil additives are added to oils during the manufacturing process to improve the performance of motorcycle oils. Below are examples of commonly used additives. Additives are often used to improve the lubrication qualities & reduce oxidation (burning) & friction, but they can also be used for simple things like changing the colour of the oil.

Additive	What it does
Detergents	Detergents improve the cleanliness of the engine, especially in hot areas. They work by holding the by-products of oxidation (burning) in suspension & in so doing prevent the oil coagulating & stop deposits building up in the engine.
Dispersants	Dispersants help control cold-sludging & also carry products that assist the combustion process
Oxidation & corrosion inhibitors	Oxidation & corrosion inhibitors reduce the rate of oil oxidation & help control any corrosion due to acids & water vapour
Anti-wear agents	Anti-wear agents protect rubbing components against wear from friction by improving film strength. This is especially good in aiding the lubrication of valve components
Pour depressants	Pour depressants lower the point at which an oil solidifies so they do not thicken so easily when cold
Viscosity-index improvers	Viscosity-index improvers help to reduce thinning (when hot) & thickening (when cold) of oils. They help control oil consumption & improve cold starting. Viscosity-index improvers enable the oil to flow like a thin oil & lubricate like a thick oil at all times.
Oiliness agents	Oiliness agents reduce the friction of heavily loaded rotating or reciprocating parts (like the fly wheel)
Anti-foaming agents	Anti-foaming agents reduce foaming, which is caused by the air in the crankcase mixing with oil under turbulence. Foaming reduces an oil's ability to lubricate & cool & increases oxidation

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