What Motor Oil Should You Use?


Never has there been an issue as hotly debated as what motor oil to use in a motorcycle. Forget helmet use, forget brand-loyalty, forget counter-steering. If you want to see an inflammed ruckus with much YELLING and many exclamation points!!!!!! ask about motor oil in a motorcycle forum.

It seems like such a simple question. And perhaps there is a simple answer: Use the motor oil that you feel meets your needs.

But how do you decide which motor oil that is?


You're going to have to do a little research. Do some reading. It'd be nice if there was some resource that simply said for motorcycle XYZ, use motor oil brand ABC in grade 123. And you may find one that does, but that resource will invariably have been at least sponsored, if not directly written, by the folks who make and sell motor oil brand ABC in grade 123. Shocking.

Owner's ManualEdit

The first thing to read is the owner's manual for your motorcycle. If you don't have one, get one. You can buy owner's manuals from:

  1. Your local authorized dealer
  2. An online vendor of OEM parts
  3. Helm, Inc. if you're looking for a Honda manual
  4. Or even eBay, if you're brave enough

The owner's manual is written by the people who know your motorcycle's innards the best, and who have a vested interest in it living a trouble-free life. (Yes, you'll buy a new bike sooner if your old bike dies young--but will you buy the same, short-lived, brand again?)

What you'll find in the owner's manual is the minimum API grade of oil to use, and a variety of weights to choose from, depending on the conditions under which you'll be riding.

This is your starting point. Don't use a motor oil that doesn't meet the specifications listed in the owner's manual. There's really no reason to, since there are a vast array of motor oils to choose from that will meet those requirements.

Online ResourcesEdit

We'll cover the basics of motor oil below. But this article is only one of many you can and maybe should read if you want to make a fully informed decision. So, here's a quick list of some good resources available online concerning motor oil in general, and motor oil for motorcycles.

  • All About Oil - Mark Lawrence has put together a detailed, yet easy to read, webpage about motor oil. Its referenced repeatedly below.
  • API Services and Grades Summary - another good webpage by Lawrence, this one summarizes the API services and grades.
  • Official API Services and Grades - the API services and grades, straight from the horse's mouth, as it were. Surprisingly, Lawence's summary is more informative.
  • Synthetic Oil Life Study - a detailed study of the longevity of synthetic motor oils in an automotive application.
  • Blackstone Labs - one of many places offering motor oil analysis, Blackstone's website gives a good explanation of what information you get from motor oil analysis, and how you can use it.


A quick note on warranties:

In the U.S., under the Magnuson-Moss Warranty Act, you are not required to use OEM products nor have service done by an factory-authorized service center in order to maintain the warranty on your motorcycle.

You are required, however, to have records demostrating that the service required in the owner's manual was performed, and that motor oil meeting the requirements in the owner's manual was used.

Basic InformationEdit

API GradeEdit

Do NOT use this oil in your motorcycle.

To the right you'll see an example of the API Service Symbol, also known as the API donut. This is on most bottles of motor oil sold in the U.S. If it isn't on the bottle, that means the oil has not been certified to meet API standards.

The API donut tells you three things:

  1. API Service and Grade
  2. SAE weight
  3. Whether the oil is "Energy Conserving"

This label is controlled by the API. Manufacturers are required to submit samples of their oil for testing by independent (from the manufacturer) labs to certify that the oil really does meet the requirements to carry the API donut, and what that donut says.

The API publishes a pamphlet explaining the donut.

Energy Conserving motor oil will increase a vehicle's mileage. However, the common wisdom in the motorcycling community is that the additives used to achieve this higher mileage is detrimental to a wet clutch, which most motorcycles sold in the U.S. have.

There is no objective evidence to support this notion. But, there are plenty of oils that are not rated "Energy Conserving," so it's probably best to err on the side of caution and not use "Energy Conserving" motor oils. Plus, it's mostly a non-issue. The vast majority of such oils are 5W-30 weight, and few if any motorcycles use that low of a weight of oil.

The API Service is the first letter of the code in the top of the donut.

  • "S" - gasoline service
  • "C" - diesel service

The subsequent letters give the particula grade of the service that the oil meets.

For gasoline service, the grades are assigned alphabetically, and any grade meets all of the previous grade's requirements. Thus, service and grade "SJ" meets all of the requirements for grades SH, SG, SF, etc. (Some letters were intentional skipped by API.)

The diesel grades are more complicated, as there are different kinds of diesel service, such as "severe duty, high speed, four-stroke engines using fuel with less than 0.5% weight sulfur" as opposed to "severe duty, two-stroke cycle engines."

Mark Lawrence has put together a nice summary of the various API grades on this webpage.

Your owner's manual will tell you the minimum API service and grade you need to use in your motorcycle. But perhaps you want to go above and beyond the minimum requirements? See the More Information section below.

SAE WeightEdit

The API donut also tells you the SAE weight of the motor oil. The "weight" of a motor oil is essentially its viscosity, or how "thick" it is. 30-weight oil is less viscous than 40-weight oil.

In multi-weight oils, such as 10W-40, the first number is the oil's "weight" at low temperatures, and the second number is the oil's "weight" at high temperatures. Multi-weight oils have mostly displaced single-weight oils in the market place because they give better lubrication at start-up, especially in cold weather, than single-weights, and yet give the same protection at higher, operating temperatures.

The details, of course, are a lot more complicated than that. Mark Lawrence's All About Oil webpage goes into those complicated details (among other things), and yet manages to be comprehesible.

Referencing back to your owner's manual, you'll find a recommend weight of motor oil, or perhaps a selection of weights depending on the operating conditions. For a street rider, in general there's no good reason to deviate from those recommended weights.

Synthetic v. ConventionalEdit

What exactly is "synthetic" motor oil?

Back in 1999, Mobil and Catrol went to the Better Business Bureau's National Advertising Division with a dispute over the use of the word "synthetic" in reference to Castrol's Syntec motor oil. It's case number 3526, but the NAD restricts access to case reports, so the details of the case aren't available. Suffice it to say that Castrol was able to continue to call it's oil "synthetic," even though its production process was more like the refining of crude oil than the true synthesis of oil from non-oil starting materials.

So, in the marketplace, the word "synthetic" is more about a motor oil's performance characteristics than about the manner of its manufacture--or its refinement, as the case may be. Again, Mark Lawrence's All About Oil webpage goes into the details of oil manufacture and the differences between synthetic and conventional oil quite nicely.

Are synthetics motor oils any better? Some people at the Paradise Garage website did their own Synthetic Oil Life Study. They did the study using General Motors V-8 engines, so the numbers don't directly translate to motorcycle use, but the results are still informative. In short, yes, synthetic motor oils do last longer than non-synthetic motor oils.

Is the added cost of synthetic motor oils worth the improved longevity (of the oil)? That's up to you.

Motorcycle Oil v. Automotive OilEdit

Up until Mobil 1 started marketing a motorcycle-specific motor oil, they would tell you that their automotive motor oils were completely compatible with motorcycles. Now that they offer Mobil 1 Racing 4T 10W-40, they no longer state that their automotive motor oil can be used in motorcycles.

Is that all just marketing hype? Maybe, maybe not. There is evidence that oil used in motorcycles wears out faster than the same oil used in automobiles. Back in 1994, Motorcycle Consumer News published some results from test conducted by John Woolum. Those tests showed, among other things, that motor oils used in motorcycles wear out faster than in cars. (A quick Google search will show a number of on-line copies of the article--they probably violate MCN's copyright, so we won't link directly to any of them.)

At the time, the results also showed no real difference between motorcycle-specific motor oils and automotive motor oils. But, that was 1994. Oil technology, motorcycle technology, and automotive technology have advanced since then.

Some motorcycle makers are now also specifying the JASO's MA grade motor oil. (JASO specifications are determined by the Society of Automotive Engineers of Japan, also known as the JSAE.) The MA and MB grades are motorcycle-specific.

If the owner's manual of your motorcycle specifies JASO MA or MB grade oil, your best bet is to use just that. If it doesn't, then it is unclear whether or not you need to use a motorcycle-specific motor oil. There are a lot of people in the U.S. who don't, and have no reported ill-effects from using an automotive oil that meets the grade and weight specified in their owner's manual.

(Note:As of March, 2007, Yamaha's Yamalube motor oil wasn't certified to either JASO grade. This is not mean to imply a problem with Yamaha, or Yamalube products, but rather as an example that even the most reputable motorcycle-specific motor oils are not necessarily certified to JASO grades. Indeed, as of March, 2007, Mobil 1's four-stroke motorcycle-specific oils are not certified to a JASO grade.[1])

OEM OilEdit

Honda does not own an oil refinery. Nor does Harley-Davidson, BMW, or any of the other motorcycle manufactures. The motor oil sold under their brand names is produced by an oil company, which makes lots of motor oil.

Considering the volume of oil that is sold as OEM, it's reasonable to assume that the oil in OEM bottles, is the same as the oil sold in other bottles. It would be cost prohibitive to develop, manufacture and package a motor oil formulation to be used exclusively as an OEM motor oil.

So, OEM motor oils are no better and no worse than other motor oils available on the market. The advantage of OEM motor oils is that you can be confident they are appropriate for your motorcycle. You can bet your bottom dollar that Honda, for example, won't be selling a Honda motorcycle motor oil that damages Honda motorcycles.

On the other hand, OEM motor oils tend to be more expensive. Does eliminating the guess-work in selecting a motor oil justify the additional cost? That's up to you.

Motor Oil AnalysisEdit

How do you really know if you're changing the motor oil in your motorcycle too often, or not often enough? How can you tell if the oil you're using is adequate? You can get valuable information to help answer those questions with used motor oil analysis.

Oil analysis is available from heavy machinery dealerships (such as Caterpillar) or from any number of labs which can be found on-line and to which you can mail a sample.

The company you use should be able to help you interpret the results you get from your analysis. There are various tests that tell you different things:

  • Trace metals - indicates how an engine is internally wearing. Most helpful when repeated test are done.
  • Particulate - indicates how well the oil filter is performing
  • Fuel & glycol - can indicate a leaking head gasket or worn rings
  • TBN (Total Base Number) - indicates how well the additive package is holding up. Helps determine if the motor oil is being used for too long, or could be used longer.
  • Viscosity - indicates how well the oil is holding up. Helps determine if the motor oil is being used for too long, or could be used longer.

Oil analysis can be expensive. Prices range from $30 to over $100 per sample. Is it worth it? Yep, that's also up to you.

Vast Motor Oil ConspiracyEdit

Choosing what brand of motor oil to use shouldn't be a stressful process. There is not a vast motor oil conspiracy working to cause your motorcycle to die an untimely death. Nor is there a conspiracy to keep secret some magic motor oil additive that let's you go 50,000 miles between oil changes, raises your mileage by 40% and increases your horsepower by 10%.

Free markets work to ensure that all motor oils have similar performance for a similar price. Yes, there are the occasional Flim Flam companies that sell inferior oil at superior prices, but they don't stay in business for long. You can rest assured that any established brand of oil is comparable to the others, and meets the grades to which it is certified.

The major motor oil companies aren't colluding to keep some amazing technology off the market. There is too much of an economic incentive to bring such an advance to the market for such a conspiracy to survive. (Economist call this the Prisoner's Dilemma.)

There is some difference between the brands of oil. But the differences are at best minor. You may be able to eek out a little more longevity, or a little more horsepower by using one brand over another. But no brand is going to give you huge gains, or cause significant damage.

Use a motor oil that is certified to the service and grade, and is of the weight, specified by your owner's manual, and you will do no harm. Beyond that, do whatever makes you happy.

External LinksEdit

Most of these links are repetitions of links earlier in this article. They're all gathered here for convenience.