Testers Tinker with Tinker Bell-sized Fuel Tank

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Metal coupons

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If you really must know how we compared the fuel additives, here are the particulars.

• Fuel sample size: 250 milliliters.

• Sample composition: E-10 gasoline with 0.03-percent seawater added. This is not enough to cause phase separation, since E-10 can hold about 0.5 percent water in solution.

• Gasoline additive dose: All samples were treated at manufacturer recommended levels for seasonal storage. If the product was not recommended specifically for seasonal storage, the routine usage dose was doubled.

• Metal sample preparation: all samples were polished and weighed to within 0.1 mg.

• Air exposure: Each jar was fitted with a vent made from 8 inches of 3/16-inch clear vinyl tubing. EPA studies suggest that this will give an amount of breathing comparable to a fuel tank with a 5/8-inch vent that is 3 feet long.

• Temperature and humidity exposure: All samples were kept outside from April 20, 2012 to May 20, 2012 in the Chesapeake Bay area.

• Post-exposure coupon inspection: Each metal sample was visually observed and re-weighed. The change in weight and any evidence of tarnish were noted.

Although change in weight ranged from a 2-milligram gain to 20-milligram loss, we did not report these values, as in most cases, they were not statistically meaningful, the value depending very heavily on the size of the few largest pits. This methodology is common in coolant testing, where weight loss on pitted samples is extremely variable. The visual results were more consistent.

The test used three controls: one sample contained no seawater, no aftermarket gasoline additive, and was sealed with a tight lid to eliminate evaporation, oxygen absorption, and water absorption; one sample contained no seawater, no aftermarket gas additive, and was vented in the same manner as the test bottles; one sample contained 0.03 percent seawater and was vented in the same manner as the test bottles, but contained no aftermarket gasoline additive.

Darrell Nicholson
Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 50 years. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him at darrellnicholson.com.