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More and more motorcycles can be seen out and about on the city streets nowadays, and many bikers are trying to prolong the motorcycling season biking allows them to get through heavy traffic quickly and efficiently. Motorcycle maintenance is not necessarily that easy, although the selection of oil available is slightly more straightforward than it is for passenger cars. Motorcycle maintenance and the way that we think about it today has become similar to car maintenance. While motorcycling used to be treated as a hobby and passion, and regular maintenance was truly celebrated, nowadays it tends to be delegated to any mechanic, not necessarily one who specialises in motorcycles. This article will help you to choose the correct oil for any given motorcycle and show you why it cannot be left to chance. 
The way that motorcycles are used has been a significant factor in the growth of the market share of oils that perform better at low temperatures. While a decade or so ago motorcycles were given winter viscosity grade oils of 15W and 20W, winter-viscosity grade oils of 5W now constitute over a quarter of all the oils used in Europe. This is because motorcycles are increasingly being used in spring and autumn, with manufacturers realising their utilitarian benefits as well as seeing a growing demand for scooters. In 2021 the number of registered scooters almost reached the number of regular motorcycles (7.0 vs. 7.8 million). It should be noted that the motorcycle market is going electric at a significantly slower pace in comparison to the car market. In 2022 there were 31,000 electric single-track vehicles on European roads, and by the end of 2023 this number is predicted to rise to about 49,000. Due to current environmental requirements, the manufacture of two-stroke engine motorcycles is almost entirely a thing of the past. Nowadays this configuration is most often used in non-homologated sports motorcycles. Environmental requirements also necessitate the use of catalytic systems in motorcycles, which has raised the bar for engine oils. 
To choose the correct oil you need to know the role that it plays in your motorcycle. The classic and most common solution is where the same oil is used for both lubricating and cooling the engine and protecting the transmission and clutch. This concept results from the limits of the external dimensions as well as the weight of the whole engine. In this case it is always necessary to use the appropriate motorcycle oil. As with oils used in cars, there are a couple of requirements that motorcycle oils must meet. The first of course are the aforementioned viscosity grade criteria. These are most frequently grades 5W-30/40 to 10W-40/50/60 or even 15W/20W-40/50. The second criteria are the quality standards. Among them the most frequently applied is the JASO standard, which simply and easily differentiates between oils for wet and dry clutch motorcycles. The first category is designated as MA and the next as MB. The JASO standards divide wet clutches into MA-1 and MA-2, depending on clutch friction. The higher the number, the greater the friction. MB standard applies mostly to oils for scooters with CVT transmissions or motorcycles with dry clutches. Failure to follow the JASO requirements may cause issues with the drive transmission in wet clutch motorcycles, as oils designed for them contain special friction modifiers. Using car oil, which reduces friction, typically results in damage to the clutch. So can you use car engine oil in a scooter? Technically speaking, the lack of a wet clutch does allow for this. Bear in mind, however, that scooter engines are under much more thermal pressure – a smaller amount of engine oil as well as having restricted cooling due to the engine being covered will create a higher oil temperature. The high oil temperature facilitates oxidation and the creation of contaminants that degrade the oil. Therefore it is really important to only use oil designed for motorcycles because of its significantly higher resistance to oxidation when compared to car oil. 
Fig. 1 A contaminated piston with a blocked ring due to excessive oxidation of engine oil
Fig. 1 A contaminated piston with a blocked ring due to excessive oxidation of engine oil 
Going back to MA grade oils, we should mention the challenges that motorcycle transmissions pose to the oil. High rotational speeds, straight tooth design and high pressures make transmission teeth susceptible to damage. The most frequent type of damage to motorcycle transmissions is pitting or micropitting of the teeth, a phenomenon that causes dents in the tooth material when the pressure exceeds the fatigue strength. This phenomenon (and others) as well as gear scuffing is described in the oil requirements of motorcycle manufacturers (e.g. BMW).
Fig. 2 Tooth damage – pitting
Fig. 2 Tooth damage – pitting 

Gear scuffing is particularly visible in transmissions operating under high pressure (high torque engines) or with high rotational speeds. The oil needed to prevent this phenomenon must be appropriate for the specific design (rotational speeds and pressures). The requirements of motorcycle manufacturers are frequently based on API standards, also typical for cars. For motorcycles these are most frequently the API SM standards and higher.   


Which oil should I choose? The density of motorcycle engine power necessitates the use of motorcycle-specific oils. Conformity to the manufacturer’s requirements is a key factor which, like the viscosity grade, should not be overlooked. Modern-day motorcycles more often require low-viscosity, energy-efficient oils. The top manufacturers of lubricants give you a choice within the required oil range, sometimes depending on the way the motorcycle is driven. Castrol offers oils for four-stroke motorcycle engines with various technologies aimed at a range of end customers. Those who are fans of powerful motorcycles may want to achieve the highest engine power while protecting the engine as it operates under maximum pressure, choosing POWER1 RACING oils with Race Derived technology or POWER1 with Power Release technology. Choosing these allows the rider to achieve demonstrably better motorcycle acceleration in comparison to their competitors. A good solution for motorcycles driven in a more practical manner is Castrol ACTEVO oil. Thanks to its active Actibond molecules it protects the engine against wear during ignition, operation and after the engine is turned off by staying on the moving components of the engine.