Car Oil vs. Motorcycle Oil

[Guest Tmartin]

I wrote this last summer. Sorry it's so long.

 

All About Oil

 

RoadBike Magazine, August 2003 Issue

 

By Tracy Martin

 

 

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Whenever the subject of which engine oil to use in your bike is discussed most motorcyclists have strong opinions. The misinformation, facts, half-truths and rumors are as thick as 60-weight crankcase goo--as the never-ending debate oozes on. Questions often come up like, “What viscosity should I use?” “What’s an API rating?” “Which brand is best?” and “Is motorcycle specific oil better than automotive oil at twice the price?” I’d like to tell you that I have all the answers to these questions--I don’t and I’d be weary of anyone who claims they do. Some aspects of engine oil are straightforward and easily understood. However the benefits of using a specific oil in any application will always be subjective. This article will provide you with a basic “lubricant” education so you can make a more informed choice when it comes to purchasing oil for you motorcycle. So hang on to your oil filter wrench and rag as we attempt to answer some of the more slippery questions.

 

Types of Oil

The basic functions of a lubricant, engine oil in our case, is to reduce friction, remove heat from various engine parts and give contaminants a ride to your oil filter where they can be safely stored until the next filter change. Designing a lubricant to perform these functions is a complex task involving a careful balance of properties both in the base oil and performance enhancing additives. To further complicate matters, if engine oil is also used in the transmission the wrong type of oil may cause a “wet” type of clutch to slip.

 

If you look up the section covering engine oil in your owner’s manual you may read something like the following. “Use only Honda/Suzuki/Yamaha/Harley-Davidson/Kawasaki oil in your motorcycle or any high detergent, premium quality motor oil certified to meet API Service Classification SF or SG. Do not use oils with graphite or molybdenum additives as they may adversely affect clutch operation.” The key word in the preceding sentence is “or” because manufactures cannot force you to use their specific oil unless they give it to you for free. Some dealers will even go as far as telling you that your warranty will be voided if another brand of oil is found in your engine. This is simply not true and a dealer can end up in court if they persist in telling you this. The Magnuson Moss Warranty Act provides the legal language that allows any engine oil to be used as long as it meets or exceeds the manufactures specifications. For more information on warranty related issues check out www.mlmlaw.com/library/guides/ftc/warranties/undermag.htm.

 

Because an owner doesn’t have to use OEM branded oil in their bike they are faced with almost too many choices. To start with, oils can be divided into two basic categories, petroleum (made from dead dinosaurs) and synthetic. These form the base stocks that are used to formulate engine oil. Synthetics can be made from either petroleum or vegetable oil feed stocks and many are designed for specific applications. Petroleum stocks are refined by a number of processes starting with the selection of crude oil, the best of which has a paraffin base. Synthetic oil is designed, not refined thus it can be formulated for the specific properties required for engine lubrication. In recent years a third type of oil has been on the market--Semi-synthetic blends which by definition are a combination of petroleum and synthetics.

 

A synthetic oil’s consistency and the “designer” approach used in the manufacturing process create several advantages over petroleum-based motor oils. These include: low temperature fluidity (they flow better in a cold engine at start up), low volatility (have a higher boiling point and greater resistance to evaporation--less oil consumption), better lubricity (less friction between moving engine parts), extend oil change intervals and higher detergent characteristics which keeps engine parts cleaner. In addition, synthetics offer high temperature stability--this is a big one on motorcycles, especially if they are air-cooled. An oil’s high temperature stability is tested using a process called “heat aging.” In this test oil is cooked at a temperature of 482 degrees F. for one hour causing some of the sample to boil off. At the end of the test the oil is graded on how much of the original sample is left. Pure synthetic oils will only loose around 6% of their volume while petroleum oils may loose as much as 25%. While petroleum based oils are good for everyday types of riding you should consider using a pure synthetic oil or semi-synthetic blend if you use your motorcycle for racing, where engine oil reaches high temperatures, short commutes (considered severe service), want to extend your oil-change intervals or just want high to use high-performance engine oil.

 

A word of caution for new bike owners. If you use pure synthetic oil while you are breaking-in your new engine it may be too slippery and not let the piston rings seat in quickly. Use a petroleum-based oil for the first several thousand miles (or whenever mileage your owner’s manual recommends for break-in) then switch to a synthetic. Diesel oils are excellent for this (see sidebar). Vintage motorcycles and synthetic oil don’t get along very well either. Old designs of gaskets, cylinder and piston ring materials are not up to today’s standards and if used in some older motorcycles synthetic oil may be burned excessively or leak through gasket sealing surfaces. Old-fashioned petroleum based oil is best for the old machinery.

 

Viscosity

Oil viscosity (weight) is the measurement of an oil’s resistance to flow, or how thick it is. The lower the viscosity numbers the thinner the oil. Motor oils are divided into single and multi-grade viscosity. Wear on engine components is greatest during cold start-up and multi-viscosity oils flow more freely at lower temperatures than single weight oils. A single grade viscosity is just that--one rate of flow regardless of temperature. For example, an SAE 10W-40-weight oil will flow like a 10-weight oil in temperatures below 30°F and like a 40-weight oil when the engine is up to operating temperature. The “W” in 10W-40, stands for “winter” not weight and SAE is for Society of Automotive Engineers. Some owners will tell you that using a higher viscosity oil will increase engine oil pressure and their right. While a higher weight oil will cause oil pressure to increase, the flow of oil through the engine’s bearings will be decreased because the oil is thicker--not necessary a good thing. Another function that oil provides is to remove heat from engine parts as it circulates. Decreased oil flow means that less heat will be removed possibly causing heat-related problems. So what viscosity should you use? The one recommended by your owner’s manual based on climate and riding conditions. In most motorcycle engines that ends up being 10W-40 or 20W-50.

 

Additives

Most engine oils contain some type of performance additives in amounts ranging from less than 1% to over 25% by volume. Oil additives help protect metal surfaces (rings, bearings, crank and camshafts, etc.) and extend the oil’s life inside your engine. Fuel and air combusting above the pistons creates acids that corrode metal surfaces and are harmful to long engine life. Acid neutralizers are often included in the additive package to counter act this process. Another additive that is used sometime is molybdenum disulfide or “moly.” This additive will help transmissions shift smoother but may also cause clutch slippage on some bikes and several manufactures warn against using oil that contain it.

 

 

API Categories

The API (American Petroleum Institute) administers the certification of engine oil in the U.S. This organization makes sure that oils meets vehicle manufactures warranty requirements. The API service symbol, sometimes referred to as the “donut” logo, is found on all containers of oil and provides information in three areas. At the top of the logo is a two-letter service rating in which the first letter states the vehicles fuel type, “S” for gas and “C” diesel. The second letter designates the oil’s quality level. The higher the letter, the more advanced the oil and the more protection it provides for your engine. For example, oil intended for use in a gasoline engine with a service rating of SL (SL is the newest category from API--2001) could be used in any gasoline engine that requires SE, SF, SG, SH, or SJ all lower ratings. The center section indicates the viscosity and if the lower portion of the circle states if the oil is “energy-conserving.” If this section is blank than the oil is on energy conserving. Energy-conserving oil may have additional friction modifiers which can cause clutch slippage in motorcycles that have a “wet” clutch or one where the engine oil and transmission oil are one-in-the same. In general, oils whose weights are on the thin side, 10W-30, 10W-20 and 5W-30 are energy conserving and should not be used in wet-clutch types of bikes. Oil’s whose weights are 10W-40, 15W-40, 15W-50, and 20W-50 are not energy-conserving and are OK for use in all motorcycles. Another symbol that may or may not be present on an oil container is the API Certification mark, or “star burst.” The starburst is found on oil intended for use in newer cars and light trucks.

 

Motorcycle vs. Car Oil

Because newer energy-conserving engine oils have been developed to reduce friction and increase mileage in automobiles they are not well suited for motorcycles having wet-clutches. As a result of the confusion created when these new oils were introduced oil companies seized this opportunity to produce and market motorcycle specific oils--some sold at a premium price. Depending on whether they are petroleum or synthetic based they range in price from $3.29 (Pro Honda GN4) to Motul’s 300V Sport for $12.95 per quart. Owner’s manuals for new bikes may recommend the use of oils with a JASO (Japanese Automobile Standards Organization) MA or MB rating. The MA rating is for higher friction applications (wet-clutch) while MB is a lower friction rating for use on dry-clutch designs like BMW, Ducati, Moto Guzzi or engines that don’t use engine oil for lubricating the clutch like Harley-Davidson. MA and MB ratings are new and don’t show up on many oil containers or in owners’ manuals.

 

Now for the $64,000 question, “Are motorcycle specific oils (especially the synthetics) worth the price when compared to automobile oil?” Well that depends on what you as a motorcycle owner are looking for. A recent two-part article published in Motorcycle Consumer News (January and February 2003) used a test that measured the average chemical composition of both motorcycle and automotive oils. Both oils that were energy conserving and those that use a winter designation of 10W or less were excluded. The test showed that while motorcycle and automotive oils produced by the same company are for the most part different in their makeup, the overall differences between bike and car oil is not much chemically speaking.

 

As far as I know there are no definitive tests that show if motorcycle oil will perform better in your bike’s engine or transmission than equivalent automobile oil. In off-the-record conversations that I’ve had with chemical engineers that work for major oil companies many say they really don’t know either. I talked with several service managers at motorcycle dealerships and none could recall an engine or transmission that self-destructed because one brand of oil was used over another. Given the oil industries past record for telling the truth (remember the gas shortage in the 70’s) I wouldn’t be surprised to find some advertising hype at work. On the other hand synthetics (both motorcycle and automobile types) are technology superior to petroleum oils and there is a great deal of documentation to back this up. With the wealth of information from the oil companies and motorcycle manufactures concerning what type of oil to use in your bike it’s no wonder that the subject of engine oil will forever be debated. If you’re still not sure what is best, read your owners manual and follow the recommendations made by the people that designed your bike. The bottom line--Motorcycles are an emotional type of hobby and having piece of mind while riding is certainly worth something. If a friend’s advice and/or an oil company’s or motorcycle manufacture’s recommendation regarding which oil to use gives you that piece of mind--buy it--change your oil and go for a ride.

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Oil Change Intervals

“How often should I change my oil?” is a common question. After initial brake-in most manufactures recommend oil changes between 4000 to 8000 miles depending on riding conditions. Taking short trips where the engine does not have time to reach full operating temperature is considered severe service and the change interval should be shortened accordingly. Conversely, riding extended distances is relatively easy on oil and traveling 6000 miles or further between oil changes is not a problem. Changing oil every 1000 to 2000 miles is a waste of time/money and it wears out the threads on your engine’s drain plug.

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Heavy Duty Oils

If you owned a fleet of 57 eighteen-wheelers, each with a $30,000 power plant under its hood, you would want oil that would help the engines to last at least 500,000 miles. With so many dollars at stake truck fleet owners don’t screw around when it comes to engine oil. Heavy-duty oils, commonly referred to as “diesel oils” are not energy conserving and offer better additive packages than most oil specified for cars. In fact diesel oils use formulations that are close to the “SG” oils that many motorcycle manufactures recommend. Their viscosity is usually 15W-40, which is well suited for motorcycles. They may have API ratings of SL or SJ followed by the letter “C” as in CF, CF-2, CF-4, CG-4, etc. Even Harley-Davidson recommends the use of oils with a CF rating when not using their house brand. They are available at Costco, Sam’s Club, WallMart and auto parts stores and are fairly inexpensive. They are excellent for new engine break-in or long term use. Some common brands are Chevron Delo 400 15W-40, Mobil Delvac 1300 Super 15W-40, SuperTech 2000 15W-40, Shell Rotella-T 15W-40 and there are others.

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Thank You (They let me take pictures of oil)

 

Twigg Cycles, Inc

200 S. Edgewood Drive

Hagerstown, MD 21740

301-739-2773

www.twiggcycles.com

 

Advance Auto Parts

591 Dual Hwy.

Hagerstown, MD 21740

301-665-1306

www.advanceautoparts.com

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Informational Sources

 

LUBRIZOL CORPORATION

440-943-4200

www.lubrizol.com

 

Motorcycle Consumer News

800-365-4421

www.mcnews.com

 

Lubelink.com

www.lubelink.com

 

American Petroleum Institute

1220 L Street

Washington, DC 20005-4070

202-682-8000

www.api.org

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[al_roethlisberger]

Thanks Tracy

 

 

Excellent and technically informative article

 

al

[Admin Jaap]