Never assume the fuel you just purchased is “fine”. Lives and millions of dollars have been lost due to screw-ups that originated at the production/supplier end of the fuel equation.
Example I: Last year, 5,000 light planes in Australia were grounded because Mobil distributed bad AvGas. Indications were “black sludge” and “white gunk” which manifested in the aircraft’s fuel strainers. It took weeks for authorities to outline procedures for identifying the problem.
Example II: A number of years ago, pilots at western airports saw bubbles in their fuel. Several pilots took off anyway — and lost power as a result. Pilots that allowed their fuel testers to stand saw the bubbles settle out … as water.
Only the most observant pilots even stand a chance of catching problems like these in the real world.
DEFENSE: Always drain a small quantity of fuel into the fuel tester — not just onto the ground. Fuel in your fuel tester can be visually examined for signs of contamination, and can even be sniffed (carefully) for the proper odor. Fuel on the ground can’t be checked for contamination … the ground *is* contamination.
Take out your fuel tester. How does it look? If your fuel tester is discolored by age, it will be difficult to pick up the difference in color between AvGas and Jet A. Heavily discolored or scratched fuel testers can make it difficult to see even particulate matter that might be contaminating your fuel system.
BOTTOM LINE: The key to catching problems is to look for them. Fuel testers are cheap. By using a clean, clear fuel tester, taking a good look and even a tiny sniff of your fuel from each and every drain — including the strainer — you will catch most fuel problems before they become expensive … or worse.