I was finally able to measure the MPG I am getting on my friction drive motorized bicycle. I have a 49CC 4-stroke engine mounted in a friction drive setup. I'm currently getting roughly 180 MPG which is freaking awesome. The bike has a one gallon tank on it. I should note that I use the bike as a motor assisted setup to greatly extend my physical cycling capabilities. I manually bike to get up to speed and use the engine to hold the speed for prolonged periods of time. It holds 30 MPH quite well. I'm trying to replace my car with my motorized bicycle as often as possible. I was raised to believe that every household must have a car but i'm curious if that's really true. Can a person get away from the insurance + license + yearly taxes on things you already own fiasco.... Hmmmm. To operate and maintain my car, I am spending a few thousand every year. The estimated max lifespan on these types of engines is 40,000 miles if treated with care. I totaled up the costs to replace all the common wear parts to be roughly $140: Wheels, Drive Roller, Piston, Rings, Clutch, Bell Rotor, and Spark Plug.