Why are there different oil weights for motorcycles?
Air-cooled V-twin motorcycle engines can get extremely hot, and they require a thicker viscosity oil with great film strength to ensure adequate engine protection. Large-displacement V-twin bikes in general, both liquid- and air-cooled, require greater film strength from an engine oil simply due to their nature of operation and the higher levels of stress they put on engine parts. However, a liquid-cooled metric bike with an inline engine configuration may be happy with a 10W-40 or even 10W-30 engine oil simply because there is less stress within that engine due to its architecture, and the engine temperatures are more controlled.
While other factors come into play when it comes to how well an oil will do its job, viscosity is perhaps the most important aspect of oil formulation. Knowing what the numbers mean can help riders choose the best oil for their bike. The first number in an oil weight is its winter weight, or how well the oil flows at cold temperatures. The lower the number (down to 0W) the thinner the fluid when cold. The second number is how thick the oil is when it’s hot. Typically, the thicker the viscosity the better the film strength or protection barrier the oil will have. A 10W-30 engine oil will flow well at cold temperatures but will be relatively thin at operating temperatures. In an air-cooled V-twin a 10W-30 would likely fall short in protecting critical components such as bearings and piston pins because its film strength would be too low.
Air-cooled V-twin engines, especially Harley-Davidson engines that fire both cylinders on the same crank revolution, demand an engine oil that will maintain film strength at extremely high temperatures. Using an engine oil that is too thin may lead to inadequate film strength at high run temperatures and this will, without doubt, lead to engine bearing wear.
How the bike uses oil will dictate what type of oil it uses as well. Some V-twin bikes have separate oil reservoirs while others have a common sump. Common sump applications require a formulation that will optimize wet clutch performance, protect gears from pitting and provide exceptional engine wear protection.
It is critical to consult the manufacturer’s oil recommendations for your bike. As stated previously, a liquid cooled metric bike will have much different engine oil requirements than a big-inch, air-cooled or liquid-cooled V-twin. Quicksilver’s line of premium motorcycle engine oils feature full-synthetic formulas engineered to protect whatever you ride, from a scooter all the way up to big-inch V-twins and racing bikes. They are all formulated with additive packages specifically-aimed at motorcycles to protect against engine wear, shear, corrosion and to enhance wet clutch operation. meet the latest JASO specifications and meet or exceed manufacturer recommendations for engine protection.