As bike manufacturers push the limits of design and technology to reduce weight and maximise engine output, the stresses placed on the lubricant has never been higher. Oil has to work harder than ever before resisting thermal degradation, keeping hot running pistons free from harmful deposits and protecting the compact gearbox and clutch for many thousands of kilometres.
Castrol has always been at the forefront of technological developments in bike lubricants, a culmination of over 110 years of history within various motorsport categories that has seen bikes pushed to their absolute limits. From the very beginnings of racing at the Isle of Man TT in 1907, through to the bikes in today’s MotoGP series, Castrol’s racing heritage has provided the perfect backdrop to develop lubricants that deliver ultimate performance and racing acceleration.
So what is so special about the Race Derived Technology in Castrol POWER1 Racing? Specifically, it has been developed from the learnings and testing derived through a long and successful association with motorsports and as a result, is formulated to reduce friction and deliver built-in protection across the critical areas of the 4-stroke: the engine, clutch and gearbox.
The 4T motorcycle engine, unlike the car engine, has a very compact oil system, where the engine, clutch and gear components are combined and use the same oil. In a car engine, the three areas are separated, with the engine and gearbox using specific oils. The ideal 4T motorcycle oil has to meet the very different requirements in all three areas of the bike: engine, clutch and gears.
INTRODUCTION: A CHANGING ENVIRONMENT
Today’s high-precision, high performance four stroke motorcycle engine provides many challenges for its engine oil.
Motorcycle engines produce a lot of power for their weight. Part of the secret lies in high engine speeds: a truck engine produces peak power at about two and a half thousand RPM and a car engine at around six thousand RPM. Modern four stroke motorcycle engines can rev up to 15 thousand RPM or more.
The circulating oil comes under huge thermal stress as it transfers heat away from low mass components under high power conditions. High piston speeds and power output generate very high temperatures - with not many places for that heat to go.
The oil plays a crucial cooling role – which demands oils with exceptionally high thermal stability.
But there are many other challenges that a lubricant must face:
- Poor quality oil can vaporise leading to a rapid rise in oil consumption - and a fall in protection.
- Compact multicylinder multivalve engines use complex oil circuitry with narrow oilways - the oil needs to be fluid enough to keep flowing under all conditions.
- Deposits can build up on the pistons and rings - the oil needs to keep these clean. All the while, the oil is carrying combustion by-products and wear metals into the sump and filter.
- Compared with truck or car engines, motorcycle engines are much smaller and lighter. Most four stroke motorcycle engines and the lubrication systems are combined so that all these areas rely on the same oil: one oil to do three different but equally important jobs - to protect the engine, gearbox and clutch.
Part 1 - What the engine needs
The need for performance and reduced noise and emissions has led to increasingly complex multivalve designs, use of advanced lightweight materials, lower tolerances, and higher precision components. Inside the engine, the main things the oil encounters are huge mechanical pressures and high temperatures
The oil has to act as a liquid bearing, carrying enormous loads. Between the cam and valve follower, for instance, huge forces are trying to tear the oil apart. No oil could withstand that attack alone - special zinc and phosphorous-based additive ZDDP is used to increase wear protection.
At the same time, it must prevent deposits building up that will stop the piston rings sealing properly: dispersant and detergent additives are needed. Fuel combustion tends to produce carbon, acids, varnish and other deposits that can eventually choke an engine. More specialized detergent, dispersant and anti-oxidant additives are required to stop the deposit build-up.
Over thousands of miles and millions of firing cycles, these additives degrade and deplete - which is why engine oil has to be changed regularly to keep it doing its job.
Temperature control is the single biggest challenge for motorcycle oil. Motorcycles use relatively simple cooling systems - compact liquid cooling - or a combination of air and oil cooling. Air-cooled bikes can easily overheat in dense city traffic and water-cooled bikes used in short journeys may never allow the oil to fully warm up. Either way, this can cause accelerated engine wear. The ideal oil has to maintain protection when hot. At the same time it has to flow easily when cold to aid for instance easy starting in the morning.
The oil has to adapt to a very wide range of operating conditions and demands: the right engine oil is one that keeps its shape and strength over time and in extremes of heat and cold. It must carry dirt yet must not oxidize or thicken, it has to be thin enough to flow easily through small oil ways when cold - yet thick enough to keep on lubricating and coating components when hot or under pressure. But four-stroke motorcycle oil isn’t just for engines - it also has to work in two other vital areas - the gearbox and clutch.
Part 2 - What the clutch needs
Motorcycle clutches are like the engines they serve - compact, high performance and highly stressed. Instead of one large clutch plate, they use a series of smaller ones, separated by rings, with springs squeezing them together. When the clutch lever is pulled, the plates are pushed apart, allowing them to slip - breaking the power connection between engine and gearbox. As the lever is released, the springs push the plates together again, allowing friction to feed power through the gearbox to the rear wheel.
Whenever that happens, those slipping and gripping plates generate an enormous amount of heat, so the primary purpose of the oil here is to cool the clutch and to prevent the bending and burning that would otherwise damage the rings and plates.
It’s a delicate balancing act between friction and slip - with the oil caught in the middle. If that oil is friction modified - as many fuel efficient car oils are - it will struggle to maintain grip between the plates and rings and can lead to clutch slip: the driving components spin without transferring all the power through the clutch to the road. The rider may not know why it’s happening - but he’ll know the clutch is slipping because he loses acceleration - probably accompanied by the smell of fried clutch plates.
If the oil friction is too high, the clutch may snatch or grab when engaged giving poor power take up - either when pulling away or during gear changes. Again, the rider will feel something wrong - because the machine will lurch or jerk as the clutch is let out. If the viscosity of the oil is too high, the clutch may drag - failing to disengage with the lever pulled in. This is a particular problem when the engine is cold and in motorcycle clutches where the operating movements involved are quite small.
Part 3 - What the gearbox needs
Just behind the clutch lies one more high-stress zone that the oil must also protect: the gearbox. The gearbox is a further area of the motorcycle where high precision meets high stress. High precision means compact design, tight tolerances and the use of finely machined components for ultimate engine performance. Increased stress comes through ever increasing speed, power and narrower gear sets. These narrow gear sets mean huge pressures between the meshing teeth - adding additional stress to the lubricant. Heat uncoils the polymers used in multi-grade oils and makes it more vulnerable to the high shearing action of the gears trying to tear it apart. Four stroke motorcycle oils demand specially selected components to resist shear and maintain load carrying capacity.
During operation, the faces of the gears scrape against each other under load: this can cause scuffing or scoring of the gears, the teeth can knock and hammer against one-another. This creates sub surface stresses within the gears that can weaken the hardening on the surface of the teeth making them vulnerable to pitting, the removal of material from the surface.
Castrol four stroke motorcycle oils incorporate phosphorous-based anti-wear additives which help to prevent metal-to-metal contact between the meshing gears.
Ultra-low viscosities commonly used in car engine oils can impact the protection and performance of the gears. In motorcycles higher viscosities are needed to provide full gear protection - but without compromising on the flow or friction properties needed for engine and clutch performance. Engine, clutch, gearbox…the ideal four-stroke motorcycle oil has to meet the conflicting demands of all three of these different areas.
castrol power1 racing
Castrol POWER1 Racing products are formulated to meet the needs of each of the critical areas by providing unique in-built performance based properties crucial to the operation of a motorcycle.
Additionally, Castrol POWER1 Racing with Race Derived Technology is proven in motorsports, reduces friction, and stays strong even at high speed to deliver ultimate performance and racing acceleration.