Safely mix two-cycle fuel and oil by first pouring the required amount of oil into a clean, empty gas can and adding the appropriate amount of gasoline. Never mix the liquids directly in the engine's gas tank, as they are unlikely to mix fully and may cause permanent engine damage.
Only mix two-cycle fuel and oil in a well-ventilated area; ideally, outdoors. Keep all open flames, cigarettes or spark sources away from the fuel and oil before, during and after the mixing process. Minimize spills and splashes by placing a funnel into the mouth of the gas tank before adding either the oil or gasoline.
Use oil specifically formulated for two-cycle engines. Most small engine manufacturers sell their own brands of two-cycle oil. However, any name brand or generic type of two-cycle oil is safe for use in these engines.
Refer to the engine's operating manual to ensure you are using the correct ratio of gasoline to oil. The three most common ratios of gasoline to oil are 32:1, 40:1 and 50:1. If you do not have the original operating manual, consider looking for a manual online or contacting the manufacturer for a replacement. In the best circumstances, using an incorrect gasoline to oil ratio prevents the engine from starting; in the worst case, it damages the engine.