I always knew it was my destiny to own a motorcycle. I grew up near the Starved Rock State Park in Oglesby, Illinois, where it seemed you could find a group of motorcyclists riding together at any time. I can still recall the distinct sound of a Harley as it fired up and the high-pitched zoom of a sport bike speeding toward the curves ahead.
Those memories would lead me to buy my first motorcycle. I distinctly remember the day I brought her home. Excited as a child on Christmas morning, I had to wait a few months before I could go on my first ride, since my purchase was in mid-February and I was living in Wisconsin at the time. The wait seemed unbearable, but over the next couple of months, I was able to research how to properly maintain my bike.
It was at this point that I became more confused than ever. The owner’s manual seemed to clearly indicate which oil to use and at what interval to change the oil, as well as how to store, winterize and get my bike rolling again in the spring. The chaos began when I joined a motorcycle forum. Everyone had an opinion on which oil was best. Since these forum members were older than I was, I figured they must have known what they were talking about.
Based on their recommendations, I headed to the local motorcycle shop and proceeded to purchase the first oil for my motorcycle. I was then stopped again by the man behind the counter, who had his own opinion on what oil would work best in my bike. Faced with many different choices of oils and their claims, I decided to go with the recommendation from my fellow forum riders.
Fast forward a few years. I now find myself in the lubrication field, gaining knowledge from various sources and applying it to plant applications. I’ve somehow become the expert my friends and colleagues come to for advice about their own cars and motorcycles. Their questions typically include which oil is best, what viscosity grade to use and if a synthetic or conventional oil is better. These were the same concerns I had only a few years earlier.
Indeed, there are many considerations when selecting an oil for your motorcycle. As with anything new, you should start first by reading the owner’s manual.
| 56% | of lubrication professionals do not know what to look for when selecting a motorcycle oil, according to a recent survey at MachineryLubrication.com |
Manufacturer Recommendations
Important details like the oil change interval should be listed inside the owner’s manual. For my first motorcycle, the manufacturer recommended an interval of one month or 600 miles for the initial oil change, which can be the most critical one in the bike’s lifespan. It allows any break-in wear and manufacturing debris to be drained from the engine and discarded.
The manual should also specify the appropriate oil viscosity for different temperature ranges. My manual suggested using an SAE 10W30 for temperature ranges of 10 to 100 degrees F. For temperatures of 40 to 120 degrees F, the manufacturer’s suggestion was an SAE 20W40. In addition, the selected oil had to meet the American Petroleum Institute’s service designation of SG or higher as well as the MA standard by the Japanese Automotive Standards Organization (JASO).
Other key findings in my user’s manual included information about not using diesel-specific oil with an American Petroleum Institute (API) classification of CD or higher. In bold letters, it stated, “Do not use oils labeled Energy Conserving II or higher.” The main reasons for this statement were because of my motorcycle’s wet clutch and the friction modifiers that energy-conserving oils use, as they can lead to premature clutch wear due to clutch slippage.
Understanding Viscosity
Viscosity is defined by the oil’s resistance to flow and shear. The higher the viscosity, the more viscous the fluid. The lower the viscosity, the easier the fluid flows. With motorcycle oils, the viscosity grade is represented by the SAE grading system. The higher the grade, the more viscous the oil.
Temperature has a significant impact on an oil’s viscosity. Take honey, for example. At cold temperatures, honey flows very slowly, meaning it has a high viscosity. If you apply a heat source, the honey will flow easier, changing its viscosity. With a higher viscosity, oil has increased load-carrying capabilities.
It is essential to understand viscosity when selecting a motorcycle oil. Viscosity is an oil’s most important physical property. The viscosity is what keeps the internal surfaces of your engine from coming into contact with each other. If the viscosity is too low, the gears inside the gearbox will come into contact and produce friction, leading to higher oil temperatures, decreased gear protection and increased wear. If the viscosity is too high, it may take longer for the oil to reach the cylinder walls, resulting in wear. Selecting the right viscosity requires a balance between the seasons, regional temperatures and the type of driving the rider will be doing.
Decoding the SAE Grading System
Rarely are monograde lubricants used for motorcycle applications. A monograde oil is represented by a single designation, such as SAE 40. These oils have a much narrower operating temperature range than that of multigrade oils.
With motorcycles and the broad range of temperatures in which they are driven, you will need an oil that can provide protection at colder and startup temperatures but also offer protection once the engine is hot. This can be achieved with a multigrade oil.
For my first motorcycle, the manufacturer suggested using an SAE 10W30 oil. The “SAE 10W” signifies that the oil will act as a 10W grade at colder temperatures. The “W” stands for winter. Having a lighter viscosity fluid is crucial on startup so that all internal components are lubricated quickly, reducing the amount of wear. The “30” in the designation is a measure of the oil’s viscosity at 100 degrees C (212 degrees F). This indicates how thick the oil will be at the engine’s operating temperatures.
Motorcycle-specific Oils vs. Automotive Oils
One of the main differences between a motorcycle engine and an automobile engine is that motorcycles typically use a combined sump for the transmission and engine. Automobile oil formulations generally have special friction modifiers blended in to increase fuel mileage and decrease wear. In a wet sump application, these friction modifiers would interfere with clutch performance. I’ve heard the argument that motorcycles have higher engine temperatures and speeds, but I don’t believe this plays a major factor in oil selection. Instead, a motorcycle oil should be chosen for the intended application or at least meet all the service designations.
In 1998, JASO introduced a rating system for motorcycle oils. Previously, the majority of motorcycle oils utilized automotive oils as a base. As automobile manufacturers began requiring more friction modifiers be used in their vehicles, these formulations caused clutch slippage and gearbox pitting. JASO specified four grades: JASO MA, MA1, MA2 and MB. The first three (with the designation of MA) signify that the oil is intended for a four-stroke motorcycle with an oil sump for the engine, gearbox and clutch. MA fluid is non-friction modified. If an oil is rated at MA, it means the oil’s test results were between MA1 and MA2 standards. JASO MB grade oil is also designed for four-stroke motorcycles but has lower friction properties. These oils are not to be used where a service designation of MA is required.
Synthetic vs. Mineral
When choosing between synthetic and mineral oils, you must understand what makes the two different. Mineral or conventional oils are refined from crude oil and separated into API classifications of Group I, II and III. The higher the classification, the more refined the oil. Due to the refining process involved with Group III mineral-based oils, lubricant manufacturers can legally market these oils as synthetic even though they do not have a true synthetic base oil.
Synthetic oils hold an API classification of either Group IV or V. Synthetics are man-made fluids with uniform oil molecules. Their viscosity generally remains more consistent across a broader operating range, which means they are ideal in colder conditions and high heat applications.
An oil’s change in viscosity with respect to a change in temperature is known as its viscosity index (VI). The higher the viscosity index, the less change in viscosity of the oil. Synthetic base oils are known to have viscosity indexes of 150 and higher.
Multigrade mineral oils are formulated with viscosity index improvers. While this makes the oil useful over a broader operating range, it can also have drawbacks, such as with the shearing of the viscosity index improver. At higher temperatures, these viscosity index improvers shear down faster and allow the oil to degrade quicker. For instance, an oil that began its life as an SAE 10W40 could break down to an SAE 10W30 or thinner.
Synthetic base stocks have few if any viscosity index improvers but are still able to achieve multigrade requirements. Lubricant manufacturers blend in more performance and longevity additives to make the oil last longer, decrease wear and provide better mileage. The improved mileage and horsepower come from the oil molecules being uniform and in reducing the amount of fluid friction within the lubricant film.
Selecting the Right Oil
In conclusion, it’s best to choose a viscosity range based on where and how you ride. For me, the perfect selection is an SAE 10W40 synthetic, as I like to get in a few last-minute rides before storing the bike for winter but also need protection for when temperatures reach 100 to 110 degrees F during summer. People who ride in Texas may require added protection on the upper end of the scale but not so much on the lower side. For those who ride up north in places like Wisconsin, an oil with a good cold range should be considered. I don’t discourage anyone from using a conventional oil in their motorcycle. The choice is completely yours. For me, I prefer the comfort of knowing that I can get a little longer out of an oil change. In the end, always try to select an oil that’s right for you and your bike.
About the Author
Garrett Bapp is a technical consultant with Noria Corporation, focusing on machinery lubrication and maintenance in support of Noria's Lubrication Program Development (LPD). He is a certifie...
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