The ratio of fuel to oil in a two-stroke engine is expressed as a ratio. For example, a 50:1 ratio is 50 parts fuel to 1 part oil. This fuel-to-oil ratio is important for two-stroke engines because the oil lubricates the piston and seals the rings in the cylinder for optimal performance.

If the ratio is too lean (not enough oil), the engine may not get proper lubrication, and damage to piston rings and bearings could occur. If the ratio is too rich (too much oil), it can result in smokey exhaust, fouled spark plugs, and excessive deposits in pistons and exhaust ports.

The average ratio for two-stroke motors varies from 16:1 to 100:1. The most common ratios for higher-performance 2-stroke outboards are; 40:1: or 3.2 fluid ounces of oil per gallon of gas, and 32:1: 4 fluid ounces of oil per gallon of gas. Some boat racing applications call for 20:1.

Once you have determined your proper fuel/oil mix, use this chart to measure out the proper amounts to keep your powerboat running strong.