I. WHAT IS GEAR OIL?
Scooter use CVT transmission, drive by belt instead of chain & gearbox and the rear wheel is driven by a transmission. Therefore, the transmission need to be lubricated to ensure the best and smoothest working of the bikes.
Gear oil is an oil containing EP additive (the main additives are sulfur and phosphorus) to lubricate gears that drive the rear wheel. They are also called transmission oils. According to the bike maintenance manual, in addition to changing engine oil, you also need to pay attention to change gear oil regularly.
Drive gears always operate hardly, so gear oil keeps them from wearing out or cracking that reduces bike performance. So gear oil has different indexes than engine oil, they have much higher viscosity.
When we need to change gear oil?
According to the manufacturer’s recommendation, gear oil should be changed every 20,000km (if the bike works in a stable temperature from 20-28 degrees Celsius, less dust and not flooded). However, Vietnam is a tropical country, so temperature varies much between time periods of the day. The air contains a lot of dust and especially the situation of bikes being flooded in the rainy season in HCMC. So the gear oil should be changed more often and sooner (every 8000km or every time after flooding of the bike).
When the transmission has loud noise, bike is inert and accelerate slowly. At that time, the transmission may have run out of oil or water has entered through the vent pipe (after washing bike or bike is flooded. When draining the oil, the oil will be milky white).
II. TYPES OF GEAR OIL ARE BEING MARKETED.
There are 2 types of gear oil for scooter being marketed according to API standards: API GL-4 and API GL-5. The main difference between GL-4 and GL-5 is the amount of EP additive. These additives prevent gears from wearing at high temperatures. GL-5 is more advanced grade, it contains 2 times higher additive content than GL-4, meets US military standard MIL-L-2105D.
Motorcycle manufacturers recommend that we should use GL-5 with index 80W90 and 80W140. These are also 2 popular types being marketed.
According to the research documents that I read and my own practical experience:
- Type 80W90 is should be used for bike that have been operating < 50,000km, then the gears in transmission are still tight together, so it just need use thin oil. Or we use it for bike operate in areas with lower temperatures (such as the northern mountains area or Da Lat) because when it operate in a low temperature, the oil will be thin less.
- Type 80W140 should be used for bike that have been operating >50,000km because then the gears in transmission have been worn and loose, so it will cause noise while operating. Thicker oil will cling on gears better and will reduce noise. Or we use for bike operate in regions with higher temperatures (such as the Middle region and HCMC). Because when it operate in a high temperature ,the thicker oil will be thin more slowly and it still ensure the quality of lubrication for the gears.
The process of changing gear oil is quite simple, the cost is not high, but if you do not pay attention to changing gear oil regularly, it will damage the transmission, then the cost of changing transmission will be higher many times than the cost of changing gear oil.