If you own a vintage or classic outboard motor, snowmobile, PWC, dirt bike or ATV with two-stroke power, it may require “pre-mix” fuel, gasoline combined with two-stroke engine oil. It’s the oil mixed with the gas that lubricates internal engine parts. Using quality oil mixed at the correct ratio is key to maintaining the performance and reliability of any two-stroke engine.
Fueling your two-stroke engine with the correct ratio is important. 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. A ratio that’s too rich (too much oil) can result in smokey exhaust, fouled spark plugs, and excessive deposits in pistons and exhaust ports. It can be tricky to get that ratio precise when adding gas and oil directly to a portable outboard motor tank or the tank of a snowmobile or dirt bike. If you are adding straight gas from a jug to a partially filled tank, there’s no way to tell how much you’ve poured into the tank. If you add gas at a filling station, you can read the amount from the pump but it could be an odd fraction that makes for a complicated calculation. For these reasons, it’s best to pre-mix two-stroke fuel in a separate container. This way you can add an exact amount of gas and oil to the jug. Then put that pre-mix into your machine’s tank.
The amount of oil added to each gallon or liter of gasoline is the fuel-oil ratio. Decades ago outboard motors and snowmobiles often required 20:1 fuel – 20 parts gasoline to one part oil – and that oil was usually just 30-weight auto engine oil. As engine materials improved and specific two-stroke oil were developed, fuel-oil ratios became leaner, and a 40:1 ratio became common for many powersports products. The 40:1 ratio was convenient because one pint (8 oz.) of oil mixed with a common 5-gallon jug of gas produced that 40:1 ratio.
Pro Tip: Mark the container that holds your pre-mix fuel to prevent accidentally adding straight gas to your two-stroke engine. If you have several two-stroke engines that require a different fuel/oil ratio, mark and use a separate container for each application.
A simple tool that makes it easy to get that ratio just right is a specialty measuring cup marked with a scale that indicates the correct amount of oil, at several ratios, for a given amount of gasoline. The Attwood Fuel Oil Mixing Bottle is one example, and has a cap so you can add oil at home and transport it to the gas station. It’s best to follow the manufacturer’s recommendation for the fuel/oil ratio, even when using modern oil in a vintage engine. Here are the basic steps:
1. Start with a clean, empty fuel container.
2. Measure the proper amount of oil and pour it into the container. The agitation of adding gas from the pump nozzle will thoroughly mix the oil with the gas.
3. Unless you plan to use all of the pre-mix fuel immediately, add a fuel stabilizer product such as Quicksilver® Quickstor® to the container. Follow the label to add to correct amount of stabilizer.
4. Now add the gasoline to the container. Quicksilver recommends the use of non-ethanol (REC 90) gasoline if it is available. When using modern oils it is not necessary to shake the container to mix the oil with the gas.
Your engine owner’s manual probably specifies two-stroke oil that meets a minimum standard. The minimum standard is just what it says, the bare minimum. Quicksilver two-stroke oils go far beyond minimum standards to provide greater protection against corrosion, carbon buildup and piston ring sticking while providing outstanding lubrication for internal moving parts under the most stressful conditions.
Quicksilver marine lubricants are formulated to maintain engine performance and reliability with uncompromising quality and durability.