B3C 4 in 1 Diesel Contamination Test Swabs Pack of 10The Mechanic In A Bottle Diesel Test Swabs are part of the multi award winning family of fuel solution products from B3C. This product range is scientifically engineered to provide a quick, easy, and effective means to TEST - FIX - PREVENT the problems associated with modern day fuels. Application: The Mechanic In A Bottle Diesel Test Swabs provide a quick and easy means to test your diesel, taking just a few minutes; they provide a visual indication and if it is contaminated by water, rust/scale, or sludge and asphaltenes. Directions:Step 1: Attach a swab to the extendable probe.Step 2: Submerge the swab into the fuel tank until it touches the lowest point at the bottom of the tank. Brush the swab across the tank bottom several times. Step 3: Shake swab; let dry for 2-3 minutes. (Do not exceed 3 minutes)Step 4: Compare the swab to the diesel & tank test Chart.