Gasoline test kits from Mechanic In The Bottle are simple-to-use. 4 easy steps. Just dip 1 of the test swabs into the gas for 10 seconds, let air dry for 2 to 5 minutes, compare swab to the chart on the canister and follow recommendations. Now you can see if the fuel is marginal or stale even though it doesn't smell that bad. (Ethonal masks the scent of decomposing fuel). 100 test swabs per can.