Global motorcycle sales are forecast to grow 7 percent this year, Infineum says, and Chevron Oronite points out that the days when passenger car motor oil could be used in modern four-stroke motorcycle engines are over.
Yet it is not just changes in engine technology that distinguish the two. The extending reach of emission regulations and demands for better fuel economy make the argument in favor of specifically formulated motorcycle oils a slam-dunk.
Riders in the United States seem to agree. According to Infineum USA, 66 percent already use a dedicated motorcycle oil, while 25 percent use a passenger car motor oil and 9 percent are unsure. Really?
Speaking at the Base Oil and Lubes Conference in Dubai, organized by Conference Connection, Patrice Estoueig, Oronites product line manager, said passenger cars and motorcycles have different lubrication needs and unique performance requirements. In passenger cars, both engine and transmission call for separate oils, each with their own lubrication system. Estoueig added that a passenger cars dry clutch system is a key difference over motorcycles. Cars are also usually water cooled, while for the most part motorcycles are air cooled, and that causes higher engine temperatures.
In four-stroke motorcycle internal combustion engines, all components share the same oil, including the clutch and transmission. MCOs have a lot more to contend in terms of shear stability and friction compared to pure PCMO (additive) packages, Estoueig said. Engine design plays a big part in lubricant formulation, irrespective of whether it is passenger car or motorcycle. But the operating regime of a motorcycle engine is significantly different from a car. The power of a motorcycle can be as much as 150 kilowatts per liter, while a car barely reaches 100 kilowatts per liter, a fifty percent difference in performance output.
Engine speeds, as measured in revolutions per minute, are also much higher for motorcycles, typically around 14,000 rpm compared with 7,000 to 8,000 rpm for cars. A motorcycles higher engine speed places more stress on the lubricant, particularly as engine temperatures increase. Higher temperatures stoke volatility, which leads to higher oil consumption. Estoueig said motorcycle oils are increasingly blended from low volatility base oils to minimize increases in viscosity.
Identifying the right performance properties for motorcycle transmission oils is crucial. Shear stability is important for gear durability, and choosing the right viscosity index improver is vital to avoiding permanent shearing. This is even more true as the market is trending toward lighter viscosity grades than SAE 10W-30 for fuel economy benefits, according to Estoueig.
The lubricants friction performance is another important attribute, as motorcycles use a wet clutch that requires specific viscometrics. Too low friction of the lubricant will cause poor wet clutch performance and you will get clutch slippage, and that can lead to power loss, Estoueig told delegates.
Still, MCOs are not the exclusive research domain of additive suppliers. Motorcycle original equipment manufacturers are responding to stricter emission regulations and demand for cleaner engines by developing oils unique to their powertrains. Harley-Davidson says its oils are engineered specifically for its products.
Harley-Davidson MCOs use premium detergents to keep engines, transmissions and primary chain cases cleaner, and are designed to meet antiwear lubricity requirements and improve seal and gasket performance, Paul James, Harley- Davidsons PR manager, commented in an e-mail. Whether its the oils or the bikes, Harley is doing something right: Last year the company added 52,000 riders in the U.S. and increased earnings per share by 5.6 percent.
India, the worlds largest motorized two-wheeler market, will soon enforce stricter exhaust emission standards that are expected to have a major impact. Bharat stage IV, similar in scope to Euro IV, came into effect in 2017, but the government plans to tighten emission standards even further. It plans to skip Bharat V and introduce Bharat VI for two-wheel vehicles next year.
Infineum USA estimates Bharat VI cuts nitrogen oxide emissions by 89 percent and hydrocarbon emissions by 72 percent over Bharat IV, but does not set CO2 emission limits. Still, the upgrade is likely to increase demand for higher quality lubricants, analysts say. The two- and three- wheeler segment is Indias largest vehicle class, with 80 percent of these vehicles under 125 cubic centimeters (the volume of the engine cylinders, which is directly related to engine power) and sales exceeding 20 million units in 2017, the latest year for which figures are available.
Shailendra Gokhale, managing partner of Mumbai-based Rosefield DAA International Consultancy, says delivering fuel economy in fuel-injected engines will be a challenge and require thinner oils, raising questions of durability. To be compliant with Bharat VI emission limits, MCOs must overcome conflicting performance objectives. The trade-off between curbing phosphorus contamination without losing gear durability is one example. Two-way catalysts will become bulkier and three-way catalysts will be expensive-catalyst protection from (phosphorus) poisoning is required.
According to Marty Meyers, marketing communication manager at Infineum USA, an on-board diagnostics system will be obligatory on two-wheelers and may further limit phosphorous levels. If so, that could prompt changes in the next JASO T903 motorcycle oil specification upgrade in 2021. The MCO needs to provide robust gear and engine protection, especially if the phosphorous level of the oil needs to be lowered, he noted.
Japans benchmark T903 standard measures clutch performance and is revised every five years. Building on the SAE #2 friction test, the 2016 T903 standard evaluated the coefficient of friction, stop-time index and friction properties of the lubricant, compared to 2011 levels.
With the exception of China, Infineum predicts strong motorcycle sales in parts of Asia, underlining the relevance of JASO. T903 analyzes three areas: dynamic friction index, which checks clutch engagement; static friction index, assessing the level of protection given to the clutch; and stop-time index, a measure of how much time it takes the clutch to engage when the lever is released. Large increases in the treat levels of friction modifiers in JASO MB 2011 oils caused oil deposits as well as stability issues, so 2016 T903 friction limits have been rolled back to 2006 levels.
Meanwhile, mindful of intensifying regulatory pressures, OEMs are focusing on reducing greenhouse gases even more by striving for better fuel economy, as CO2 emissions are directly linked to fuel consumption. As with passenger car applications, they are developing thinner oils to help achieve this end.
Although SAE 10W-30 is the current reference point, OEMs are considering introducing SAE 5W-30 and SAE 0W-30 grades in the future, according to Estoueig. For additive companies such as Chevron Oronite, the fundamental shift in market dynamics in favor of lighter grades poses formulation challenges, particularly in regard to limiting engine wear. Friction modifiers are currently touted as a way to reduce metal-on-metal friction without losing paper-on-steel friction-important for optimal clutch performance-but they can cause clutch slippage in some instances.
Despite the common goal of achieving better fuel economy with light viscosity grades, the gap between passenger car and motorcycle engine oil applications has widened. PCMOs are designed with low viscosity-specifically high temperature, high shear viscosity-in mind. Low HTHS is a proven characteristic for fuel economy. However, in the case of MCOs there is still a need to lubricate the transmission, with tests showing that low HTHS causes gear pitting in some situations.
Chevron Oronite has developed its own proprietary engine durability test that detects differences in performance between MCO and PCMO, which was run with SAE 10W-40 oil formulated with API Group II base oil. The test set out to measure performance of a PCMO against an MCO formulated with an additive package designed specifically for motorcycle oils. The test ran a Honda engine for 100 hours at full open throttle to evaluate detergency and oxidation. The parameters for assessing detergency were piston and land ratings. Oxidation was gauged by total acid number (ASTM D664) and viscosity increase (ASTM D445).
According to Estoueig, the MCO showed better oxidation performance and better detergency under the test conditions, with good deposit control on the piston over the PCMO product. Comparing pistons, we could see the piston skirt was quite similar between the two, but the best differentiation was in the varnish on the piston and crown, showing a clear difference in performance in favor of the MCO product.
The Road Ahead
Infineum USA forecasts ICE motorcycle sales will grow 7 percent per year through 2020, but the predicted rise in e-mobility makes the market difficult to gauge in the medium term. By 2025, the additive company estimates sales could be anywhere between $22 billion and $55 billion, with China being the dominant market. Lower costs, reduced pollution and ease of mobility in congested cities will make e-bikes and e-scooters popular, particularly in urban areas. Regulators will also have to grapple with new technologies other than electrification, including supercharging and start-stop systems.
Despite the push for sustainability, ICEs remain a top priority for motorcycle OEMs. Several initiatives aim to prolong their appeal, including turning to smaller, lighter and low-friction components to satisfy fuel economy requirements. Automatic transmissions, which offer riders improved shift smoothness and easier low-speed maneuverability, will be supported by the inclusion of super-charging and turbocharging to enhance acceleration.
Development of current and future motorcycle oils will require application-specific testing to confirm performance as well as compliance with JASO specifications and emission regulations. Ultimately, MCOs must benefit the end-user with a lower total cost of ownership. A tailored MCO product should provide improved oil consumption and fuel economy and longer drain intervals, Estoueig concluded.
For increasingly demanding riders, that translates into more carefree time on the open road.