Engine Oils basically all consist of a base stock (base oil) enhanced with various additives, particularly antiwear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers. Before we get into the best motor oil for your motorcycle, we need to take a look at each of these things separately and analyze the benefits they provide.
Best Motor Oil Base Oils
Base stocks (or base oils) come in 6 different groups. For the purposes of this article, we’ll only be discussing groups 2-5. These are the groups virtually all engine oils are made from currently.
Group II base stock is composed of fractionally distilled paraffinic mineral oil stock that has been solvent dewaxed and
hydrocracked to further refine and purify the oil. Shell™ Rotella® and Pennzoil™ Purebase® are two examples of Passenger Car Engine Oils
made from Group II base stocks.
Similar characteristics to Group II base stocks, Group III base stocks have higher viscosity indexes. Some Group III
base stocks with VHVI are sometimes referred to as Group III+. Group III base stocks are produced by a wide range of
processes, such as further hydrocracking of Group II base stocks, or by chemically modifying slack wax, which is the
end-product of the dewaxing process, which improves the VI. Some Group III+ oils are created by highly processing oil
into what have been called “Severely Hydrocracked,” “Chemically Modified,” or “Semi-Synthetic.” Castrol™ Syntec® and
Valvoline™ Durablend® are oils manufactured from Group III base stocks.
This group is reserved for one type of synthetic oil made up of a class of molecules called PAOs (polyalphaolefins).
Contrary to popular misconception, the molecules which make up PAO and many other synthetic oils originate in crude
oil. In the case of PAOs, they are created by polymerizing olefin molecules obtained from the cracking of wax molecules.
In many cases, these wax molecules are a by-product of mineral oil dewaxing processes. Fully-synthetic Mobil One®, Castrol® Power1®
and Amsoil™ are examples of oils made from a primarily PAO base with some Group V esters added to improve
additive solvent and seal swelling performance.
Group V is the catch-all group for any base stock not described by Groups I to IV. Examples of Group V base stocks
include the old naphthenic base stocks, silicones, polyol esters, polymer esters, PAG (polyalkylene glycols), and PFPAE
(perfluoropolyalkylethers), as well as others. Since there is nothing in common between most of the oils lumped together
as Group V, it makes no sense to discuss them as a group. Instead, a few single types of synthetic oils in Group V will be
discussed individually. Synthetic Redline, Motul, and Maxima 4 Extra/Ultra are example oils with a Polyol Ester base.
In the chart above, you can see the various specs that set each group apart from one another. The best motor oils will have low volatility (helps it perform consistently over time), med-high polarity (better clinging to metal for less wear on cold starts, better able to trap & remove contamination) low pour point, higher flash point, and of course an affordable price tag. For most motorcycle riders, this will be something in the Group IV category. Group V oils tend to perform better, but are exponentially more expensive. Let’s face it, most of us don’t have the budget for a $100+ oil change.
Other Considerations in picking a Best Motorcycle Oil
If you have a metric bike with a wet clutch, or you need oil for a primary case with a clutch in it, you’ll want to look for a JASO MA Rated Oil like Shell Rotella T4 Conventional, T6 Synthetic, Castrol® Power1®, Synthetic Redline, Motul, and Maxima 4 Extra, and most motorcycle specific oils will fit the bill. Just make sure it has a JASO MA rating, and no “Energy Conserving” properties listed on the API donut.
If you’re looking for an engine oil to put in your Harley, or other motorcycle that separates the engine & clutch/primary/transmission oils, you don’t need to worry about the JASO MA rating, you can use energy conserving oils which tend to be “extra slippery” to pick up a little extra power/mpg (by reducing friction losses) instead.
What Weight of Engine Oil is Best for my motorcycle?
Most motorcycles have a specified oil weight. Actually, a range of acceptable weights depending on the temperature you’ll be riding in. Check your owner’s manual to see which weights are safe for your bike.
Oil weight is a term used to describe the viscosity of an oil, which means how well it flows at a specific temperature. The Society of Automotive Engineers (SAE) assigns a viscosity number, or weight, to oil based on its flow at 210 degrees F, which is roughly the standard operating temperature for most motors. The higher the number, the thicker or slower flowing it is, which changes the nature of how it coats internal engine components and protects against heat and friction. This means a 30 weight oil flows more quickly than 50 weight oil, but doesn’t offer quite the same level of protection at higher operating temperatures or in stressful conditions.
You’ve probably noticed that most bottles of oil actually have two numbers on them, separated by a “w.” These are called multigrade oils, and they are unique in that they have been engineered to offer not just one, but two weights. Confused? Here’s how it breaks down. The “w” stands for winter and indicates that the lubricant in question has a different viscosity, or different flow characteristics, based on temperature. For example, a 5w30 oil weight rating means that on cold start-up — even at subzero temperatures — the oil flows like a 5 weight oil. However, once warmed up to 210 degrees F, it functions as a 30 weight oil. This is accomplished through the inclusion of unique additives in the mixture.
The API Donut
Another symbol that commonly appears on motor oils is the API “donut.” API stands for the American Petroleum Institute, which offers a stamp of approval to help customers find engine oils that meet the minimum standards set by engine and vehicle manufacturers.
This symbol has three parts: the top half of the circle, which indicates the API service rating, the center of the circle, which displays the SAE viscosity, and the lower half of the circle, which tells you the oil’s energy-conserving properties.
API Service Standards
You may have noticed the images above have a few different API Service rating examples, here’s a breakdown of how those work:
Current API Ratings For Gasoline Oils
- SN: For vehicles manufactured after 2010
- SM: For vehicles manufactured between 2004 and 2009
- SJ: For vehicles manufactured between 2001 and 2004
All the other API ratings (between SH and SA) are obsolete. So even if you have an engine that’s older than 2001, you may want to avoid these ratings. It’s always wiser to use the most current API rating for two reasons:
- Fresh motor oil
- Compatibility with your engine
Motor oil with any of the current API ratings should still be good to use. If you’re using motor oil with an SJ API rating, proceed with caution. There’s a chance that the oil has expired.
Current API Ratings For Diesel Oils
- CJ-4: For four stroke high speed diesels manufactured after 2010
- CI-4: For vehicles manufactured between 2002 and 2010
- CH-4: For vehicles manufactured between 1998 and 2002
Any other API rating is obsolete. It’s always best to use a current rating to ensure reliable lubrication in your engine.
Muck like the DOT ratings of brake fluid which we discussed in another article, you can use newer API rated oils in an older engine, but you don’t want to use an older API rating in a newer engine.
Putting It All Together & Choosing the Best Motor Oil
Now that we know what makes one engine oil different from another, we know we need to look for a few qualifications:
- We want a Synthetic Groip IV or V oil for better long-term performance.
- A JASO MA or MA2 rated oil when dealing with a wet clutch.
- An Energy Conserving oil when the clutch isn’t a consideration.
- We want an API rating compatible with our bike.
For many metric cruisers at stock or near-stock power levels, a HDEO (heavy duty engine oil) like Rotella T6 is a good balance that checks all of the boxes. Last time I saw an independent test sheet, it had better wear protection and long-term performance than many motorcycle-specific oils, and virtually all dealership oils.
Just check the label for the JASO MA rating before purchasing, because some manufacturers (not Shell, as of yet) have changed their formulas recently and are no longer JASO MA rated. Also, if you have a catalytic converter on your bike (and plan on keeping it), the high anti-wear additive levels in HDEOs will eventually take a toll on the catalyst.
If you want a good motorcycle-specific oil instead, or a good Harley Primary oil, check out Lucas High Performance Synthetic.
It’s USA-made, and greatly exceeds the quality of basically all of the oils you could get from your local motorcycle dealership.
In my Sportster, I like to run energy conserving Mobil1 15w50 in the crankcase, and Lucas in the primary/trans. The 15w50 may or may not still be energy conserving. There’s been rumors of the formula changing.
What’s your favorite motorcycle engine oil and why? Feel free to share by leaving a comment below!