I changed the oil in my trike yesterday myself, it was a chore but I got er done. I used Mobil1 M/C 10-40 Racing 4T oil. The transmission whine in lower gears is nearly gone, even after the engine warms up. When I bought it the dealer said they had just changed the oil to Honda syn oil, but after hearing the difference I am beginning to think they probably put regular oil in it to save the dollars. I bought this oil at Walmart, about 10 bucks a quart. I would happily pay the dealer to change it if I could get exactly what I want there.