How We Tested
For precision, and to work with quantities of fuel more suitable to a lab than a gas dock, we used metric, rather than U.S. liquid, volume measurement. We dosed 500 milliliters of untreated E10 fuel with excessive water to see how long it could hold off phase separation. Then we similarly overdosed eight 500-milliliter fuel samples, each of which was mixed with a different fuel treatment. To that treated fuel, we added water in 0.5-milliliter increments of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 and 5.0 milliliters and noted the results. Phase separation began for all treated samples at 2.5 milliliters--0.5 percent or 12,500 ppm, proving the efficacy of using stabilizers. So at the end of our test, an average 25 milliliters of crud — 5 percent of the fuel supply — sank to the bottom of the graduated cylinders we used for testing.