The engine in your car is a 4-stroke. And while most of today’s motorcycle engines are 4-stroke types as well, there are still some 2-stroke engines out there, especially when it comes to scooters and off-road bikes. Chainsaws, outboard engines, and weed-whackers also use 2-strokes. This sort of engine needs to have oil mixed in with the fuel. How much oil? Most owner’s manuals will tell you, but ratios between 32:1 and 40:1 are common. Thus, your mix is 40 parts gasoline to one part oil. If you’re working with the metric system, it’s easy: 10cc of oil to 400cc of fuel. Imperial measurements are a little less intuitive: an ounce of oil (think shot glass) to a quart of gasoline is about 32:1. A gallon of fuel is 128 ounces. At a 40:1 ratio, that means you’ll need 3.2 ounces of oil. Pour the correct amount of oil and gasoline into a bottle or can, shake vigorously, and pour it into your fuel tank. No separate bottle or measuring cup? Pump the straight gas into your fuel tank, add what you think is the correct amount of oil, fit the gas cap and slosh the bike as violently as you can to mix it together. Too little oil will result in engine damage; too much will foul the plug and stop the engine, but without doing permanent damage. No oil at all? You’re out of luck.