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ADV Prepping10 Synthetic Oil Myths and Misconceptions Debunked

10 Synthetic Oil Myths and Misconceptions Debunked

 Motul’s top oil guru answers all your burning questions.

Published on 09.13.2019

With many adventure bikes and dual sport motorcycles requiring synthetic motor oil these days, there are a lot of myths swirling around about what to use, or not to use. And let’s face it, synthetic oil isn’t cheap. So the more we can clarify the misconceptions, the more-informed decisions we’ll make about how to best use our hard earned cash. One thing is certain, we wouldn’t be enjoying the incredible performance of modern machines today if it weren’t for advancements in motor oil. 
We talked to Motul’s top oil guru, Joey Cabrera, to help separate fact from fiction and answer all of our burning questions about synthetic oil. As the National Technical Director, Joey’s job is to travel the country advising companies and consumers on the right oil to use for different applications. He’s also a rider with several bikes in the garage, so he’s familiar with the concerns of motorcyclists. Joey shares his thoughts below  on some of the common questions and misconceptions in the adventure motorcycling community.
Motul Synthetic Oil Dakar Rally Sponsor
Some synthetic oils have been proven to increase horsepower in some cases.

1.) If you change your conventional oil regularly, you don’t need synthetic

Joey Cabrera: There are many benefits to using synthetic motor oil that you won’t get from just regular oil changes. Synthetic oils protect engines better under heat conditions and flow better under extremely cold conditions. Not only will it make your engine run cooler but also smoother because of how synthetics are designed. Synthetics are known to withstand heat better and not breakdown at high temperatures or high loads. Certain Synthetic oils, like our racing product, have also proven to increase horsepower in some cases. 

In addition, you can expect longer drain intervals, a better detergent package to clean up impurities, smoother shifting, and improved overall levels of performance. Several of our synthetic oils include Esters as well, which offer extra protection for cold startups by leaving a fine film on all ferrous metal components to prevent premature wear of high-stressed parts like cam lobes.

Changing synthetic motor oil

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2.) Never use synthetic oil to break in an engine

JC: This is true. It is typically better to break in an engine with conventional oil because it will allow the piston rings to seat faster. It’s not that you can’t use a synthetic to break in an engine, it is the fact that higher-quality synthetics are more slippery and the process to break in an engine takes longer. 

Most engine builders prefer using a conventional oil for the initial break-in, and use a conventional oil for the next 300-600 miles before switching to a synthetic. Motorcycle manufacturers are also likely to use conventional oil for the first fill in a new motorcycle engine and break in, even when synthetic is recommended. When the bike is returned to the dealer for its first service (oil change) after 600 miles, then the bike is filled with synthetic.

3.) Once you switch to synthetic, you can’t go back. And never mix!

JC: It is a myth that you cannot return to using conventional oil after using a synthetic. If this were true, then every oil company would need to have a disclaimer on the bottle giving a warning to the consumer. It’s perfectly safe to switch between or mix synthetic and conventional oil. In fact, there are many products on the market that are synthetic/conventional blends.

Synthetic blends are largely a cost versus benefit decision. A product like Motul 5100 is designed for the customer that uses his/her bike more for commuting and doesn’t want to pay the price of a full synthetic. It blends traditional mineral oil with more technologically advanced synthetic oil, so you get many of the advantages of improved additives and refinement. They are less expensive than a full synthetic motor oil while offering higher performance than a conventional oil.

4.) ‘Synthetic’ Motor Oil is artificially created oil that isn’t derived from petroleum

JC: Synthetic oil is a lubricant consisting of chemical compounds that are artificially made. The base material, however, is still overwhelmingly crude oil that is distilled and then modified physically and chemically. The actual synthesis process and composition of additives is generally a commercial trade secret and will vary among producers.

The word “synthetic” describes a process and not so much the material. For example, white sand is synthesized into glass, but glass is never called ‘synthetic glass.’ Synthetic oils are like designer oils. It all starts from crude but through different processes, we end up with different groups designed for different applications. 

synthetic oil made in a lab
The word “synthetic” describes a process and not so much the material.

There are five different groups of base stocks used in engine oils. Groups I and II  are mineral oils (i.e. conventional petroleum oil), while Group III, IV and V are synthetics. A Group III synthetic is more refined than mineral oil and typically hydrocracked (higher pressure and heat) to achieve a purer base oil. Group IV (PAO) is refined mineral oil that undergoes a special process called “synthesizing.” Generally speaking, Group IV performs better than Group III oils in handling heat, oxidation, low temperature start ups, and has a higher film strength and viscosity index (ability to flow). However, with today’s technology, some Group III oils perform as well as a Group IV.

Motul’s Synthetic Group V (Esters) oils are mostly made from vegetables, minerals and animal fatty acids. Esters are much more expensive because the ingredients are collected from nature, then get synthesized (which is a very expensive process). Group V Esters have all the advantages of a Group IV PAO, plus they can handle even higher temperatures. When Esters are burned, they leave far less coking deposits and are attracted to metal parts with an electro-chemical bond five times stronger than mineral oil. 

5.) If your motorcycle manufacturer recommends synthetic oil, it’s still ok to use conventional

JC: If the manufacturer recommends synthetic then you should use what the manufacturer recommends. Engineers design motors to run with the type of oil that meets the engine’s specific tolerances and characteristics.

Keep in mind high-quality oil isn’t just for maintenance, it’s also insurance. This is especially important for those who ride far away from civilization like adventure riders do. What if a rock hits your radiator or your water pump fails, or you lose oil from a cracked side cover in a fall off-road? What would you rather have in your engine – a conventional oil that burns up very quickly and carbonizes, or a synthetic oil that can handle higher running temperatures (325° F to 360° F)?

Deciding what motor oil to use.

Considering the high-performance engines and the type of riding, I would strongly advise using a full or semi-synthetic oil for most dual sport and adventure motorcycles.

6.) There’s really no difference between motorcycle and car engine oils

JC: Car oils contain friction modifiers and are formulated with a focus on reducing friction between moving parts in an effort to improve fuel economy and reduce emissions. Also, these oils contain detergent additives, whose ash content is relatively high. If used in motorcycle engines, these could result in the formation of deposits on the piston crowns as well as the valve train. Deposits can cause pressure build up, leading to perforation and burning of components. 

Motorcycles, on the other hand, use the same oil for both the engine and the gearbox. Motorcycle oils are therefore uniquely formulated to offer protection for engine components and the transmission gears. They need to be slippery enough to protect the engine, but not too slippery that they affect the wet clutch found in most motorcycles.

synthetic oil designed for diesel engines.
Car oils are designed for a completely different set of engineering requirements. You should always use oil made specifically for motorcycles. 

Motorcycle oils are designed to strike a good balance between clutch performance, and engine and transmission protection – something that is not considered in the manufacturing of car oils. When car oil is used in a motorcycle the clutch may not fully engage, leading to clutch slippage and power loss.  

To avoid issues, always use a motor oil designed for motorcycles with JASO rating (i.e. safe to use with a wet clutch). JASO ratings are MA, MA1 and MA2 with MA being the most slippery and MA2 offering the best clutch performance. There is also a JASO MB rating designed for automatic transmissions like those found in scooters (don’t use with a wet clutch). 

7.) Any synthetic oil with a JASO rating is always ok to use

JC: I often come across riders who use automotive based synthetic oil in their bikes in an effort to save money. A JASO rating alone isn’t enough to make it safe for use in a motorcycle engine. Car oils are designed for different types of engines with different engineering requirements. A motorcycle engine has smaller components, runs at different temperatures, has different tolerances, and its oil must work with the gearbox and clutch – so it is important to use an oil that was designed to work in the environment the engineers intended it for. 

Look for JASO MA2 rating.

Also, keep in mind that some oil manufacturers may claim a JASO rating on their product but aren’t certified by JASO. A JASO “certified” oil has undergone testing to be allowed to display the certificate on the bottle. Check the JASO website to see if the oil you are considering is listed as certified by JASO. 

8.) So you are low on oil in the middle of nowhere. Any oil will do…

JC: If you have limited options for oil in a remote area, first try to avoid using any oil that doesn’t have a JASO MA, MA1 or MA2 rating. There is no issue with mixing a conventional oil with synthetic, but try not to mix in higher viscosities than are recommended for your motorcycle. Whenever you have to mix in something non-optimal to get out of your current situation, make sure you change it the first chance you get with the proper oil for your bike.

motorcycle oil selection may be limited in remote areas.

9.) Using synthetic oil can cause oil leaks

JC: With modern motorcycles, you should not have any issues with oil leaks using synthetics. However, oil leaks may occur with older motorcycles that have a lot of miles. The problem isn’t the oil though. The powerful detergents in synthetic oil do an admirable job of cleaning out the crud within the engine. As it does this, it also locates the weak sections of your old gaskets and cleans the crud out that was previously preventing any oil from leaking out.

What’s the solution if you’ve made this mistake? Well, you can’t just change back to conventional oil, it’s going to leak through the old gaskets as well. You’ll have to replace the gaskets to fix the leak. If an old motorcycle engine has been rebuilt with quality gaskets, then there is no problem with using a synthetic or semi-synthetic. If it hasn’t, then it’s a good idea to stick with a conventional product.

10.) The best place to get advice about oil is to post a question on the forums

JC: Any time you post a question about oil in a forum or on social media, you are bound to get a lot of different opinions – many of which may not be the best advice. If you have questions about what oil to use for a specific application, we at Motul are always happy to share our expertise. You can contact us through the Motul website and your questions will be forwarded to either myself or one of our other oil techs.

Author: Rob Dabney

Rob Dabney started a lifelong obsession with motorcycles at the age of 15 when he purchased his first bike – a 1982 Honda MB5. Through his 20’s and 30’s he competed in off-road desert races, including the Baja 250, 500 and 1000. Eventually, his proclivity for exploration led him to dual sport and adventure riding. Rob’s never-ending quest to discover what’s around the next bend has taken him on Adventures in Mexico, North Africa, Europe, and throughout the American West. As a moto journalist, he enjoys inspiring others to seek adventure across horizons both near and far.

Author: Rob Dabney
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18 thoughts on “10 Synthetic Oil Myths and Misconceptions Debunked

    • Kawasaki doesn’t require synthetic oil for KLRs so nothing wrong with running conventional oil, especially if you ride easy and change more frequently. There are some reasonably priced synthetic blends you might consider too that offer a little extra protection for cold starts, high temps, etc. Just added insurance to help prevent failure, especially if you don’t know how well the previous owner maintained the bike. It’s a cost/benefit decision every rider has to make.

  1. Good food for thought ! Old rule of thumb “grease & oil is cheap “ when it comes to any piece of machinery. Originally grease base consisted from a olive oil mineral oil (shale extraction) tallow (animal fat) soap base eventually mixed into a crude oil mixture. The technology has come a long way in 160 plus years. Valvoline being the first brand name oil product developed by a doctor following the American Civil War
    One area that should be considered when it comes to type/brand/grade of oil use as to the engine specifications is variants of ambient tepature changes and how it can effect cold starts. A engine using cartridge type filters, whether water cooled or equipped with a oil cooler should be allowed to warm to operating tempature at a moderate to low rpm and not the staggered erratic snapping of the throttle to avoid filter collapse. Synthetic mixes is engineered to compensate and safe guard in these situations.
    Although, prolong terms between changes can also cause similar problems. Variations in crankcase volumes can also determine change cycles before the oil viscosity values drop.
    A good read supporting Robs interview.
    https://mil-comm.com/lubricants/the-ultimate-historical-timeline-of-mechanical-lubrication/

  2. I agree with most of the stuff here and the point of crazy opinions when you ask oil questions online .I’m just not sure taking everything an oil salesman says as fact . Would have been nice to hear from an engineer with less sales motivation .

      • Group III is a controversial class as they are derived from crude oil like Groups I and II, but their molecules have been so changed by severe processing that nowadays they are sold as Synthetics. Most people in the US now accept Group III as synthetic but the discussion remains heated among purists.

      • The law says group III is synthetic. Some lawsuit back in the 90’s against castrol syntec or something made it this way…….

    • As a mechanic with 18 years of experience working for factory race teams I can tell you he is correct. In fact not only hp but torque output.

  3. Any recommendations on air cooled 4 strokes? Would like to try a synthetic or semi syn on a XR650L. Just did a 300 mile loop going over two 12000 ft passes and oil temps reached 300 degrees at times using standard 10-40.

    No problems at all but temps were alarming – no oil cooler. Would a synthetic give better temp protection without clutch problems or should I stick with conventional oil and just add an oil cooler??