By Brian O’Neil

Insight on modern fuel: Modern fuel today contains up to 10-percent ethanol (E10). Most modern power equipment is designed to handle E10, but problems arise when fuel is left to stand for prolonged periods of time and especially with older equipment not designed to handle any ethanol. The high amount of oxygen present in ethanol naturally decays gasoline, which is organic. Imagine if you left a jug of milk in the fridge and then left another jug of milk outside in the middle of the summer — open. Obviously, the milk outside will decay much faster.

This is what happens to the fuel in your fuel system. Even under good conditions, ethanol-blended fuel can deteriorate, causing hard starting and the formation of gum or varnish in your fuel system (see Figures 1-3). This can happen in as little as 60 to 90 days.

Did you know that ethanol can have devastating effects on power equipment? Ethanol-blended gasoline can damage plastic and rubber fuel-system components, particularly in older power equipment not designed to tolerate ethanol. Even newer equipment experiences these problems if it sits for prolonged periods with fuel in the tank (i.e. 3 months or more). In Figure 4, the bowl gasket became brittle and non pliable. In Figure 5, the 2-cycle carburetor diaphragms are stiff, which causes starting and running problems. The primer line (Figure 6) and return lines (Figure 7) are brittle, causing fuel to leak.

Ethanol also attracts water (hygroscopic), which causes the already corrosive nature of this blended fuel to become more corrosive. If enough water is absorbed, phase separation will occur. This is more prone to happen over the winter months when the temperature drops below freezing. Why does this happen more often over the winter months? Ethanol can hold more moisture in suspension in warmer temperatures, but over the winter when it gets cold, the ethanol cannot hold as much moisture in suspension and phase separation begins. Phase separation looks like water at the bottom of a fuel tank, but in reality, this is mostly ethanol with a little bit of water. Did you know that it only takes about a tablespoon of water in a gallon of gas to begin phase separation?

This mixture is extremely corrosive and is what destroys carburetors and fuel-system components. In 2-cycle equipment, this will destroy the engine if run on this almost pure ethanol at the bottom of the fuel system. E85 (a fuel mixture of 85-percent ethanol and 15-percent gasoline) and E15 (a fuel mixture of 15-percent ethanol and 85-percent gasoline) may be good for automobiles, but they are not approved for use in power equipment by the U.S. Environmental Protection Agency (EPA) and can cause serious damage to the engine or fuel system (Figure 8).

2-cycle phase separation: Figure 9 and Figure 10 show an engine that has been destroyed from phase-separated fuel. Ethanol is hygroscopic (absorbs water); the vial pictured in Figure 11 is from the fuel tank of the engine in Figure 9 and Figure 10. In Figure 11, the fuel on top is gold in color because 2-cycle oil will only bond with the gasoline. The octane is also lower because the ethanol has separated from it and bonded with the water below. Approximately 3/4 of the clear fluid in the bottom of the vial is ethanol.

The ethanol-water mix settles in the bottom of the fuel tank and is picked up by the fuel system, then delivered to the carburetor. The engine ran on this ethanol mixture, causing it to run extremely hot with no lubrication. This damage occurs in only a few minutes of operation. The engine also ran out of control, which poses serious safety concerns for the equipment operator.

4-cycle phase separation: The carburetor, pictured in Figure 12 and Figure 13, suffered from severe phase separation. More than likely, rainwater entered into the fuel system, creating the severe corrosion you see. This carburetor cannot be repaired and must be replaced.

Engine failure from varnished fuel: The piston and crankshaft assembly, pictured in Figure 14, came from a 2-cycle engine that ran on stale fuel. The engine was hard to start and had low power. It ran long enough to gum all of the internal components, including sticking the rings.

The majority of the general public is unaware of “phase separation” and that ethanol-blended fuel may often be the culprit causing some of the problems they experience with their power equipment. However, great strides are being made in the effort to educate the public about the negative effects of ethanol-blended fuels, and general awareness is on the rise. Yet there is still great opportunity to increase ethanol education, and ethanol education is the key to solving this dilemma.


 Brian O’Neil is Chief Business Development Officer for B3C Fuel Solutions. B3C utilizes advanced synthetic technology to develop new and improved products to protect engines from the adverse effects of today’s modern fuels. B3C’s core products can be found at retailers, as well as lawn and garden dealers and distributors throughout the United States. For more information, call (843) 347-0482 or visit All photos provided by and remain property of B3C Fuel Solutions.