Do not get lazy. If there is a problem with your fuel, there will be a problem for you — the only questions you need to ask are: when will it happen and what will it cost? Remember the stakes. Pilots can avoid some very costly problems down the line if they stick to one simple RULE:
Check your fuel at every takeoff for quantity and contaminants — whether you are flying a rental plane or your own.
Why (Part I): If you own the plane, you know what you put in the tanks, right? What this misses is that the plane was flying. Water that “swished” away from the drain may have migrated back. Now it’s waiting near the lowest point in the tank — right where the fuel pickup is — to be sucked into the lines that feed your engine. Fortunately for you, there’s a drain down there too. Use it.
Why (Part II): Fuel caps can leak. If your plane flies through a chance shower, or gets wet while on the ground, water can seep through cracks in your fuel cap O-rings and collect in your tank. If you only check your tanks when you add fuel, you will miss this. It will not, however, miss you. When it comes to water in your fuel, you are either predator or prey: catch it or it will catch you when you least expect or can least afford it to.
BOTTOM LINE: Being proactive about checking your fuel before each and every flight — for quantity and contaminants — will give you the framework to identify and stop problem sequences before they stop your engine. You will also attack one of the biggest causes of off-field landings and ensure the safety of your plane, yourself and the people who fly with you.