MotoMojo: Keep Your Motorcycle Runnin’…With the Right Oil

Apr 22, 2015 View Comments by

Keep Your Motor Runnin'...With the Right OilWhat You’ve Always Wanted to Know About Motorcycle Oil

Motor oil is the lifeblood of our precious engines, but how much time have you spent learning what kind is best for them? Over the years, motor oils have evolved and so have motorcycles. The American Petroleum Institute (API), International Lubricants Standardization and Approval Committee (ILSAC), and Japanese Engine Oil Standards Implementation Panel (JASO) all have specifications for motor oils. Two-stroke engines are now mainly seen in off-road motorcycles. The API has a classification “TC” for two-stroke oils designed for various high-performance engines such as those on motorcycles, snowmobiles, and chain saws with high fuel-oil ratios. Two-cycle engine oils designed for API Classification TC address ring-sticking, pre-ignition, and cylinder scuffing problems.

Nearly all motorcycles today have four-stroke engines, and most motor oils are designed for them. Motor oils meeting the JASO T 903:2006 standard are classified into four grades: JASO MA, JASO MA1, JASO MA2, and JASO MB. The classification is based on the JASO T 904:2006 clutch system friction test. In order for a motor oil to meet any of these JASO standards, it must fit one or more of the following specs: API SG, SH, SJ, SL, SM or ILSAC GF-1, GF-2, GF-3. The API uses specifications for automotive gas engines such as SG, SH, SJ, SL, and SM. The current API specification is “SN,” which was introduced in October 2010 for 2011 and newer vehicles. ILSAC uses GF-1 through GF-5 (the latest).

Viscosity is a fluid’s resistance to flow, which affects oil’s ability to lubricate and transfer heat. Too thick and it won’t flow and lubricate at low temperatures such as cold starts. Too thin and it may fail to protect from metal-to-metal wear at high temperatures. Viscosity grades, also known as “weights,” were set by the Society of Automotive Engineers (SAE), an example would be SAE 20W-50. Grades with a “W” in them are so-called multi-viscosities; for example the 20 is the weight in cold (winter) weather, and the 50 after the W is the weight when hot. Grades that don’t have a “W” are single summer-temperature viscosities.

There is an optimal viscosity for every situation, and the closer the oil is to this, the better. Air-cooled engines typically reach higher oil temperatures than liquid-cooled engines, and you may find oils which are specifically listed for air-cooled bikes. Generally, these oils have a higher viscosity to maintain sufficient film strength at high temperatures. Liquid-cooled engines are usually less demanding and can use oils with a lower viscosity. Always look up the temperature-viscosity chart in the owner’s manual and follow that.

All motor oils have additives that protect from corrosion and wear, plus detergents to keep combustion byproducts in solution. Synthetic oils and combinations of both synthetic and conventional oils (synthetic blends with no more than 30 percent synthetic oil) have become popular due to their superior stability, lubrication qualities throughout the temperature range, and ability to go longer between changes. Synthetic oils, which are made from polyalphaolefins oil esters rather than from distilled crude oil, are more stable and resistant to high temperatures than conventional oils.¬†Synthetics are priced significantly higher than conventional oils, and blends of the two types are typically priced in between. Some motorcycle makers even call for synthetic oils to be used exclusively. If the manufacturer of your motorcycle recommends only synthetics, it’s best to follow these instructions.

Often, conventional oils are fine, particularly if you don’t run the engine very hard or operate in extremely hot or cold weather. In cases where the oil needs to be changed frequently due to dusty conditions, short trips, or other reasons, a considerable amount of money can be saved by using conventional oils.

You can’t go wrong by using motorcycle-specific oils, which are now also available from major oil companies. However, many motorcyclists dislike the significantly higher prices of motorcycle-specific oils and prefer to buy their oil at auto parts stores or mass marketers for price and convenience. It is possible to save money by carefully choosing the right oil for your use and still protect your engine.

Many motorcycles run engine oil through their transmissions, which creates a high “shear” force on oil molecules that isn’t a concern in auto engines. Many oils contain polymers, called viscosity index (VI) improvers, needed to make multi-viscosity oils such as 20W-50. Polymers are subject to some degradation in a transmission, but full-synthetic oils typically have less polymer content than conventional oils, and hence degrade less.

In addition, lots of bikes have “wet” clutches, which run in engine oil. Generally, only lighter-viscosity oils such as 5W-20, 5W-30, and 10W-30 are labeled as “energy conserving.” Heavier viscosities such as 5W-40, 5W-50, 10W-40, 15W-40, 15W-50, and 20W-50 oils are not “energy conserving” and can be used for most four-stroke motorcycle engines. Read the container and avoid the “energy conserving” oils. All oils have friction modifiers, but energy conserving oils typically contain more, which may cause clutches to slip under normal use. Most quality non-energy conserving automotive oils should work if your clutch is in good condition. Castrol warns that 5W50 Syntec is not for motorcycle use because of high levels of friction modifiers. If your motorcycle manufacturer specifies oils meeting JASO or other motorcycle-specific oil specifications, with no reference to API SG or similar specs, follow recommendations to protect the warranty.

Many API SL automotive oils contain lower levels of zinc/phosphorous extreme pressure additive (ZDDP) than prior SG, which protects against metal-to-metal contact. This is normally only a concern for older engines with non-roller valve lifters, which rub across the cam face. Automotive racing oil generally meets SG requirements and has higher levels of additives like ZDDP and should work fine in older motorcycles. Certain “heavy-duty” oils, often called “diesel oils,” have higher zinc levels than oil that is only rated “SL.” These oils, which are typically 15W-40, are rated SJ or SL plus CH-4. They are closer in formulation to motorcycle-specific oils and to the “SG” oils that many motorcycle makers suggest using.

Manufacturers recommend certain oil change intervals, which must be followed to maintain warranty coverage. I recommend changing oil at least that often, and retain proof of purchase of oil and filters or work orders to document proper service. Castrol, Mobil, Pennzoil, Quaker State, and Valvoline now sell their own motorcycle-specific oils at very competitive prices, and they can be bought at auto parts stores and online retailers. However, it’s good to patronize motorcycle shops if you want them to be there when you really need them.

By Ken Freund


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