BACKGROUNDHonda has been involved in environmental issues for

many years. Since the 1980's many environmental issueshave been highlighted that need to be dealt with on a globalbasis. Fundamentally, they strive to deal with these issueseven before they are recognized as environmental issues. Assuch, they have published a corporate objective to achieve a30% CO2 emissions reduction as compared to 2000

emissions levels in all engines they produce by 2020.1

The motorcycle market has been continuously growing,especially in Asia where 80% of the world's motorcycles aresold. This further highlights the value of reducing CO2emissions of motorcycles.

One way to reduce CO2 emissions is to improve fuelefficiency. This strategy has been employed in theautomobile segment with design of lower friction engines andmore fuel efficient engine oils. Engine oil fuel efficiency canbe improved by reducing viscosity and formulating with lowfriction chemistry.

2013-32-906320139063

Published 10/15/2013Copyright @2013 SAE Japan and Copyright @ 2013 SAE International

doi:10.4271/2013-32-9063saefuel.saejournals.org

Improving Fuel Efficiency of Motorcycle OilsBrent Dohner, Alex Michlberger, and Chris Castanien

Lubrizol Corp.

Ananda GajanayakeLubrizol Japan Ltd.

Sumitaka HiroseHonda R&D Co., Ltd.

ABSTRACTAs the motorcycle market grows, the fuel efficiency of motorcycle oils is becoming an important issue due to concerns

over the conservation of natural resources and the protection of the environment. Fuel efficient engine oils have beendeveloped for passenger cars by moving to lower viscosity grades and formulating the additive package to reduce friction.Motorcycle oils, however, which operate in much higher temperature regimes, must also lubricate the transmission and theclutch, and provide gear protection. This makes their requirements fundamentally very different from passenger car oils.Developing fuel efficient motorcycle oils, therefore, can be a difficult challenge. Formulating to reduce friction may causeclutch slippage and reducing the viscosity grade in motorcycles must be done carefully due to the need for gear protection.Additionally, in high temperature motorcycle engines, low viscosity oils are more prone to oil consumption, which willnegatively impact fuel economy. They also may cause more deposit formation, which can reduce overall performance.

The lowest viscosity grade oil currently recommended by Honda for motorcycle applications is a 10W-30. This studydescribes the development of a new 5W-30 motorcycle oil to deliver enhanced fuel efficiency in motorcycle engines. Thekey target of this development was to deliver enhanced fuel efficiency with a 5W-30 while not compromising any of theperformance of the current high quality 10W-30 oil. Testing was conducted to validate oil consumption, clutchperformance, oxidation resistance, wear protection, gear protection, and engine cleanliness in modern Honda motorcycleengines. In all aspects, the newly developed 5W-30 oil performed equivalent to or better than the high quality 10W-30reference oil. As the final proof of performance, the new 5W-30 oil was compared with the 10W-30 reference oil in amotored motorcycle engine friction torque test and clearly demonstrated the desired enhanced fuel efficiency.

CITATION: Dohner, B., Michlberger, A., Castanien, C., Gajanayake, A. et al., "Improving Fuel Efficiency of MotorcycleOils," SAE Int. J. Fuels Lubr. 6(3):2013, doi:10.4271/2013-32-9063.

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Figure 1. 2020 Product CO2 Emissions ReductionTargets

Figure 2. Growth in Asian Motorcycle Market2

While this strategy has been effective in the automotivesegment, it has limitations in the motorcycle segment.Motorcycle oils operate in a much higher temperature regimeand must also lubricate the transmission and the clutch, andprovide gear protection. This makes their requirementsfundamentally very different from passenger car oils.Developing fuel efficient motorcycle oils, therefore, can be adifficult challenge.

OIL DEVELOPMENTThe objective of this oil development was to create the

most fuel efficient API SL / JASO MA2 quality low viscositymotorcycle oil, that had all the performance qualities of acurrent SAE 10W-30 oil. Two additional criteria were addedas new development targets for this oil. The oil was to beformulated with a target 43 cSt kinematic viscosity at 40°C tomaximize fuel economy and the oil was also to be formulatedto a target of 12% NOACK to control oil volatility. Lowerviscosity improves fuel efficiency while lower volatilityenables the oil to maintain its fuel efficiency throughout usein the engine.

As a result, an SAE 5W-30 oil was developed to meetthese criteria. The formulation shape and oil properties of thisoil are shown in table 1.

Table 1. Formulation and Properties

The oil was formulated with all Group III base oil tooptimize the viscometrics within the 5W-30 grade whileminimizing the volatility to ensure fuel economy durability.In addition, a unique polymethacrylate (PMA) was used as aviscosity modifier. It was chosen because PMA's are knownto improve fuel efficiency. In addition, this particular PMAwas chosen due to its shear stability. Utilizing a very shearstable PMA enables formulating to lower viscosity withoutthe oil shearing out of grade. Finally, an additive approachwas developed to provide the enhanced durability needed fora 5W-30 motorcycle oil in modern engines. In addition tocomponents present to meet the API SL performance level,several motorcycle specific components were utilized suchas:

a. chemistry to enhance clutch performance andminimize clutch slippage.

b. thermally stable detergent system designed for hightemperature motorcycle applications

c. gear protection components for gear pitting protectionin this low viscosity 5W-30

d. additional antioxidant chemistry for high temperatureconditions as well as to provide fuel economy durability bypreventing oxidative thickening

e. low volatility zinc dialkyl dithiophosphate to minimizecatalyst poisoning, hence further reducing emissions.

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This oil was then tested in a series of bench tests designed

to evaluate some basic properties such as corrosion protectionand deposit formation. In all cases, the oil performance wasoutstanding.

Table 2. Bench Testing Results

Then the clutch friction performance was evaluated usingthe JASO T903:2011 test procedure. The oil easily met thecriteria for JASO MA2, the highest JASO performance levelfor a motorcycle oil.

Table 3. Clutch Testing Results

Since motorcycle engine oil is also lubricating thetransmission gear box, the low viscosity oil was also checkedfor gear protection performance. The load carrying capacityperformance was evaluated using the ASTM D5182 (CECL-07-95) test procedure in a FZG test rig. The results in thistest show the 5W-30 candidate had equivalent performancecompared to the high quality 10W-30 reference oil.

Table 4. FZG Gear Test Results

Next, fatigue life performance was evaluated using aneedle roller bearing pitting test on a uni-steel bearing tester.

Thrust needle roller bearings are used to simulate gear fatigueconditions due to their sliding operation

Figure 3. Weibull Probability Plot

In this test procedure, NSK FNTA2542 thrust needleroller bearings with reduced rolling elements are set up in anoil bath at 120°C to operate under maximum contact stress of2.2 GPa and the peripheral speed of 2.6 m/s at the mid-pointof needle rollers. The occurrence of pitting on needle rollersis detected using an accelerometer and the number of cyclesto fail is recorded. Pitting life is evaluated based on L10 andL50 life indices derived by Weibull probability analysis onmultiple (N =6) test run data.

Figure 3 shows the Weibull probability plot comparingfailure probabilities of the candidate versus reference oils.Accordingly, the candidate oil shows significantly betterfatigue life in L10 and equivalent fatigue life in L50. Thisfurther supports equivalent gear pitting protection of thecandidate 5W-30 compared to the 10W-30 reference oil.

ENGINE TESTSIn addition to bench tests, four engine tests were used to

validate oil performance. In each engine test, a ‘reference’test was conducted using the current high quality 10W-30 oilto determine acceptable performance. Table 5 summarizeseach engine test.

Table 5. Test Engine Summary

Valvetrain Wear TestingThis test uses 110 cc air cooled engine (Engine 1) driven

by an electric motor. Engine speed is low to induce boundary

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lubrication and accelerate wear. The test is operated under aproprietary procedure. All valvetrain parts including thecamshaft lobes, rocker arms, rocker arm pins, valve tips andadjuster screws are carefully measured before and after thetest and compared to evaluate wear.

Figure 4. Valvetrain Wear Test Rig

Both reference and candidate oil tests showed only tracewear, with many components having no measurable wear atall. Each camshaft lobe was measured for maximum lobeheight (diameter) in three places as denoted in the figure 5.

Figure 5. Lobe Measurement Locations

Table 6. Camshaft Measurement Data

Viscosity Increase TestingLike the valvetrain wear test, this test also uses the same

110 cc air cooled engine, but this engine is fired, and installedon an engine dynamometer. The purpose of this test is todetermine the ability of the engine oil to resist viscosityincrease due to high temperature and high load operation.During the evaluation, the engine is operated at wide openthrottle (WOT) and oil temperature is maintained atapproximately 145°C. The engine is operated at these harshconditions until the oil level drops to a predetermined level.No additional oil is added during the test and oil samples aretaken every two hours and tested to determine viscosity.

Figure 6. Viscosity Increase Test Rig

Kinematic viscosity at 100°C for both the reference oiland for the candidate oil, can be seen in figure 7. Clearly, thecandidate oil offers much more resistance to oxidativethickening than the reference oil. The candidate oil alsoshowed lower oil consumption, as indicated by the longer testduration.

Figure 7. Kinematic Viscosity at 100°C

In addition to viscosity measurements, elemental analysiswas conducted on each oil sample. From this analysis, %

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phosphorous retention was calculated. The candidate showedmuch higher % phosphorous retention than the reference oil.3

Figure 8. Phosphorus Retention

Phosphorous retention is an important in order to maintainwear protection. Also when phosphorous volatilizes andleaves the engine, it can poison exhaust catalysts. Whenexhaust catalysts become poisoned, the emissions increase.While the objective of this development is improved fuelefficiency, the ultimate goal is emissions reduction. Thereforethis oil may have additional emissions benefits beyond thosefrom the improved fuel economy.4,5

Transmission Gear DurabilityTwo different tests were used to evaluate the lubricant's

ability to protect transmission gears from wear (measured aspitting). The first uses an air cooled single cylinder engine,while the second uses a four cylinder liquid cooled engine.These two engines are very different with regards toarchitecture and operation, and thus place uniquerequirements on engine oil.

The single cylinder engine is carbureted and utilizes asingle overhead camshaft with sliding contact rocker arms.Rolling element bearings are used for the crankshaft,camshaft, and transmission shafts. The four cylinder engineemploys fuel injection and other modern design elementssuch as liquid cooling, journal bearings for the crankshaft andcamshafts, bucket and shim tappets, and lighter components.All of these improvements optimize the engine for high speedoperation. By contrast, the design of the single cylinderengine lends it to slower operation, but at highertemperatures. The candidate oil must perform equally well inboth engine types.

Overall Performance Evaluation - AirCooled Engine

The 230 cc air cooled engine (Engine 2) was chosen foroverall performance evaluation. The engine was removedfrom the motorcycle and installed in an engine test rig, and

operated under a proprietary procedure for a long duration athigh engine oil temperature.

All critical engine components were measured, weighed,and inspected before and after the test with the emphasis ontransmission gear durability. To reduce variation, speciallymade transmission gears were used for this test.

Transmission gear wear was evaluated by measuring andsumming the pitted area on each tooth of the mainshaft andcountershaft gears. The following tables show the totalamount of gear pitting for each set of mainshaft andcountershaft gears.

Table 7. Fifth Gear Pitted Area

This total pitted area represents only 4.9% and 5.2% ofthe total gear tooth area for the reference and candidate tests,respectively. Therefore, the 5W-30 candidate oil offers anequivalent level of protection as the 10W-30 reference oil.

For the majority of the test, the engine is operated in 5th

gear, as a result, the pitting observed on the fourth gear setwas much lower, and can be seen in table 8.

Table 8. Fourth Gear Pitted Area

This total pitted area represents only 0.08% and 0.38% oftotal tooth area for reference and candidate tests, respectively.Pitting is low but present on both mainshaft and countershaftgears which were operated with the reference lubricant.Interestingly, the candidate gear set only exhibited pitting onthe mainshaft gear, with no pitting observed on thecountershaft gear. Additionally the majority of the pitting onthe mainshaft gear occurred only on one tooth.

Engine components were also evaluated for varnish andcarbon deposits. Components were rated in accordance withASTM rating scales and methods. In this scale, a rating of 10represents a perfectly clean component. Table 9 summarizesthe deposit and varnish ratings.

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Table 9. Deposit and Varnish Ratings

The 5W-30 candidate oil has shown equivalent depositcontrol when compared to the 10W-30 reference oil.

Overall Performance Evaluation - LiquidCooled Engine

The test engine chosen for the overall performanceevaluation was a 600cc four cylinder liquid cooled engine(Engine 3). The engine was removed from the motorcycleand installed in an engine test rig. The engine test wasconducted under proprietary conditions which are much moresevere than any normal drive cycle. In Figure 9, the testengine can be seen operating at these test conditions, note theextremely high exhaust temperatures which lead to glowingred exhaust pipes.

Figure 9. Glowing Red Exhaust Pipes

Again, all critical engine components were measuredbefore and after the test to determine wear, and again,emphasis was placed on transmission gear durability.

Table 10. Sixth Gear Pitted Area

Both reference and candidate oil protected thetransmission gears with very low amounts of pitting found onthe reference test and no instances of pitting observed on thecandidate test gears.

Table 11. Fifth Gear Pitted Area

Once again, the transmission gears experienced very lowlevels of distress, with the candidate oil exhibiting noinstances of pitting. In addition to transmission gear wearcontrol, both the reference and the candidate oil exhibitedexcellent wear protection on camshaft lobes, tappets,bearings, and bushings throughout the engine.

Fuel Economy EvaluationAfter demonstrating that the candidate oil could meet all

of the performance durability targets, it was necessary toquantify its fuel economy benefit. To do this, a friction torquetesting (FTT) rig was developed. The rig uses an electricmotor to drive Engine 1. A high precision torque meter wasinstalled between the engine and motor to facilitate torquemeasurement. The engine was driven to seven differentspeeds (3,000 RPM to 9,000 RPM) and high speed torquedata was recorded at five oil sump temperatures (60°C, 80°C,100°C, 120°C and 140°C) at each speed. This produced 35unique operating conditions that were then analyzed forreference and candidate oils. After each oil was tested, a highdetergent oil was used to thoroughly flush the engine beforethe next test.

To increase the confidence in test results, repeat testswere conducted for both reference and candidate oils andstatistical analysis was performed on the generated data. Outof the 35 test conditions, the candidate significantly reducedtorque and power loss when compared to the reference in allbut two conditions.

The torque necessary to maintain engine rotation at eachcondition set is a measure of the frictional losses within theengine. The oil that exhibits the lower torque therefore offersa fuel economy improvement.

Data can be analyzed and displayed in both empirical andrelative manners. Empirically, torque loss (or power loss ifrespect is given to engine speed) can be plotted againstengine oil temperature for each engine speed, as shown infigure 10.

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Figure 10. Average FTT Empirical Data

Data can also be analyzed in a relative sense bycomparing the candidate lubricants performance to that of thereference oil. This is done by calculating the average frictiontorque loss across each speed for both lubricants, thendetermining the percentage difference between the two oils.This analysis can be viewed in table 12.

Table 12. Average Friction Torque Loss Data

The candidate oil outperforms the reference oil across allspeeds and temperatures thus reducing torque loss by about3%.

Due to typical operating conditions seen by singlecylinder air cooled engines, particular attention was given tothe oil sump temperatures of 120°C as the most critical

condition. Plots of relative friction torque reduction at variousspeeds can be seen in figure 11.

Figure 11. Demonstration of Improved Fuel Efficiency

The candidate lubricant clearly offers reduced friction andthus improved fuel efficiency when compared to thereference.

SUMMARYIn keeping with the objective to reduce CO2 emissions, a

project was undertaken to develop a new oil to improve thefuel efficiency of motorcycles. By consuming less fuel, theemissions will be reduced.

The project was focused on developing a new lowviscosity, fuel efficient motorcycle oil, while matching orexceeding the engine durability provided by a high quality10W-30 motorcycle oil. As a result, an SAE 5W-30 oil wasdeveloped to meet these criteria. This development utilizedGroup III base oil, PMA viscosity modifier, and an additivepackage specifically designed to deliver superior motorcyclefuel economy.

Laboratory screen tests were initially used for oildevelopment. The oil developed was then evaluated inmodern motorcycle engine tests. These engine testsdemonstrated that engine durability was not compromised bymoving from a 10W-30 to this 5W-30 motorcycle oil.

Finally, friction torque testing clearly showed a frictionreduction, hence the fuel economy benefit of this new oilwhich increased with lower engine temperature and higherspeed.

REFERENCES1. http//world.honda.com/environmental/report/download/index1.html2. Data provided by Honda from databases of JMVA: Japan Mini Vehicles

Association and AIRIA: Automobile Inspection & RegistrationInformation Association

3. Calculation of %P retention done in accordance with the ILSAC GF-5specification.

4. Bardasz, E. A. Schiferl, E. Nahumck, W. Kelley, J. Williams, L. JSAE20077288/SAE 2007-01-1990: “Low Volatility ZDDP Technology: Part1 - Engines and Lubricant Performance in Field Applications”

5. Bardasz, E. A. Schiferl, E. Nahumck, W. Kelley, J. Williams, L. SAE2007-01-4107: “Low Volatility ZDDP Technology: Part 2 - ExhaustCatalysts Performance in Field Applications”

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