Here's What Could Happen If Water Gets In Your Gas Tank
We may receive a commission on purchases made from links.
The automotive industry is awash with all kinds of alternative fuels for internal combustion engines, from LPG to ethanol, fryer oil to hydrogen — there is even a biofuel made from an invasive seaweed. But despite pervasive urban myths to the contrary, one thing an engine won't run on is water. If you get water in your gas tank, it can cause your engine to run very badly, or not at all, and can even damage and corrode your fuel system, including the fuel pump and injectors.
Water, one of the most common contaminants in engine oil, also has a nasty habit of finding its way into gas and diesel systems, either through condensation, when moist air cools to form water droplets, or infiltration, when water seeps into the fuel. This can happen in a number of ways, including from a faulty or missing gas cap, a leaking seal in your fuel system, filling up in high humidity or rain, or filling up from a contaminated supply.
Most gas stations store their fuel in underground tanks, and while these supplies are — or at least should be – carefully filtered and monitored for quality, water can still get in. If you are unlucky enough to fill up with a tank of this contaminated gas, your car will let you know within minutes of driving away by sputtering, surging, misfiring, or conking out altogether. You may even get the dreaded engine warning light.
While water in your gas will make your car run like a hairy goat, it's not going to cause catastrophic engine failure. But it can cause corrosion and damage over time, so it is best to identify the problem and deal with it sooner rather than later. Along with the common symptoms of poor starting, rough idling, stalling, and hesitation under acceleration, a further indication is fuel that smells bad. Although if you're not in the habit of sniffing gas, this may not be a failsafe diagnosis.
Fortunately, a more accurate DIY method is available in the form of water detection pastes, such as this one from Amazon. You apply the paste to the end of a stick, dip the stick in the fuel tank, and if it changes color — usually to a bright red, blue, green, or pink — then yes, you have water in your fuel. Be sure your stick reaches to the bottom of the tank. Water does not mix easily with gasoline or diesel, and will instead settle at the bottom, leaving the fuel floating on top.
Once you have a positive diagnosis, you need to drain and clean your fuel tank. This is not without its risks — not only of explosion, but of further contamination. If your DIY skills are not up to the task, engage a professional who can perform a full fuel system flush. If you think your gas station sold you bad gas, it may be worth taking these extra steps to seek compensation.
