String trimmers are a wonderful tool for lawn and garden care, but they have a few requirements which may be unfamiliar to you if you haven't worked with them before. One of those requirements is the need for mixed fuel.
Mixed Fuel Definition
All gas-powered engines need both gasoline to make the engine turn, as well as lubricating oil to ensure the engine moves smoothly without overheating. Many larger four-cycle gasoline engines, such as in your car, have separate reservoirs for the fuel and the motor oil. You top off the fuel tank whenever it gets low and top off the oil reservoir when it gets low.
However, many smaller gasoline engines do not have a separate reservoir for the oil. Your Echo string trimmer's engine is an example. Yet the engine still needs that lubrication to function smoothly and avoid overheating. In these 2-cycle air-cooled engines, a specialty form of motor oil is added directly to the gasoline in specific ratios. This provides for both combustion and lubrication. This blend is known as a mixed fuel.
Mixed Fuel Specifications
The fuel and oil used in Echo equipment must meet certain standards. According to a fuel information sheet available on the Echo-USA website, the fuel must be 89 octane or better, and contain no more than 10 percent ethanol. These requirements ensure that the mixed fuel burns correctly within the engine, and contains enough detergents to keep the engine and carburetor free of varnish buildup.
Echo also stipulates that the oil must also meet certain standards, from two different organizations. The oil must have L-EGD certification from the International Standards Organization, which is listed on the oil label as ISO-L-EGD. Secondly, the oil must also have M345 FD certification from the Japanese Automobile Standards Organization, which is listed on the oil label as JASO M345 FD. These standards ensure that the oil is suitable for air-cooled, 2-cycle engines which operate at very high speeds and temperatures, such as in a string trimmer. Other types of motor oil are not formulated to meet these performance criteria.
Echo operators manuals also state that any high-quality oil may be used, as long as it is formulated for 2-cycle, air cooled engines, and meets the ISO-L-EGD and JASO M345 FD standards. Any oil which does not meet these criteria can void the Echo warranty.
Mixed Fuel Ratios
Echo used to specify a variety of ratios for its air-cooled, 2-cycle engines, including 32:1 and 16:1 blends. However, the company now specifies a 50:1 ratio for all their 2-cycle, air cooled engines, even if the original equipment manuals specified a different ratio. Echo states that improvements in oil formulations allow for this new 50:1 ratio for all their equipment.
If you have lost your Echo string trimmer owner's manual, they are available online on Echo's website.
Mixed Fuel Preparation
The easiest way to blend your fuel is within a separate fuel storage can, rather than in the line trimmer's fuel tank. Most Echo line trimmer fuel tanks are quite a bit smaller than one gallon in size. Trying to calculate the amount of oil to add to such a small fuel tank may result in errors. By blending the fuel and oil in a separate storage can, you can measure out exact and convenient quantities of both fuel and oil.
In addition, by mixing the fuel and oil in a separate container, you can more readily ensure they are thoroughly mixed. Simply fill the fuel container with half a gallon of fuel, add the oil and mix. Add another half gallon of fuel, mix again, and you're done.
It's a good idea to mark the fuel storage container as having a mixed fuel, so you'll never have to wonder if the fuel is already blended or not. Be sure to completely use up the fuel in the storage container prior to refilling, such that old fuel does not mix with new fuel. Then each time you refill the fuel storage container, add another batch of oil.
Mixed fuel can separate if left undisturbed for long periods. Always slosh the fuel around right after mixing in the oil, and again right before adding it to your string trimmer's tank.
Both fuel and oil-based lubricants are flammable. Never fill a fuel tank, blend fuel, or store either fuel or oil near an open flame or intense heat source.
- Echo-USA Support: Operator Manuals, Safety Manuals, Parts Catalogs and Safety Videos
- Echo-USA FAQ: Fuel/Oil Mixture
- Echo-USA FAQ: Engine Oil Requirements
- Echo-USA FAQ: Fuel/Oil Ratio
- Echo-USA Operator's Manual: Grass Trimmer/Brush Cutter model SRM 225
- 3cyl.com: Understanding Modern 2-Cycle Lubricants
- Echo-USA FAQ: Fuel Requirements
- Echo Red Armor Engine Oil Information
Kathryn Kerby has been gardening, farming and/or ranching since the 1980s. She currently owns and manages Frog Chorus Farm in Washington state. Ms. Kerby has written extensively about gardening and sustainable agriculture, with articles in Permaculture Today and various sustainability newsletters. She is author of "The Chicken Coop Manual."