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'. '.strtoupper('t')his 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. directionsstep 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'. '.strtoupper('b')rush the swab across the tank bottom several times. step 3 shake swab let dry for 2 3 minutes'. '.strtoupper('d')o not exceed 3 minutesstep 4 compare the swab to the diesel tank test chart.