Mercury - Quicksilver 75W-140 Motorcycle Transmission Oil Heavy-Duty Gear Protection High-Performance V-Twin Formula 8M0128390. Overview. When you ride a big V-twin, you get used to the feeling of raw strength beneath you - that steady rumble, that confident pull, and the sense that every gear change sets the tone for the road ahead. But those engines, especially the ones running separate gear cases, don't just need oil. They need a transmission fluid that can absorb heat, pressure, and long mil