Gasoline out of the pump to most drivers is like water out of the spigot. They assume that water is water and gas is gas, and that, in both cases, some regulating body has made sure that what is going into our stomachs and in our gas tanks is the right stuff.

Not so fast. Just as we find contaminated water from time to time, we also find contaminated gasoline. And just like bad meal can play havoc on the human digestive system, so too can bad gas cause expensive, unpleasant problems for your vehicle.

WHNT-TV out of Huntsville Alabama recently reported on a Trinity, Ala. couple whose car was acting terribly after gassing up, and then wouldn't start at all the next morning. Celestra Gordon and her husband were told by their mechanic that the fuel injectors were ruined after processing gasoline that had been contaminated with water.

After discovering the vehicle's warranty would not cover the damage, the Gordons contacted the gas station. The station shut down the pumps, and is reimbursing the Gordons for the repairs, reported WHNT.

The Gordons were lucky. It's not easy to prove a case of contaminated gas, as Clarence Davis of Texas found when he faced about $700 in repair bills and related costs.

Davis gassed up his car at a Bedford, Texas Kroger station last year. Afterward, his engine sputtered and died. A mechanic diagnosed it in writing as having water contaminated gasoline. Davis, reported the Dallas Fort Worth Star-Telegram, reported it to the Kroger as well as Texas Department of Agriculture, which regulates gas and gas pumps. The state inspector certified that Kroger's gas met state standards, and the Kroger disputed Davis's claim that it had water in its tanks, asserting that gas is tested multiple times a day and that there is a shutoff built in to the pumps if bad gas tries to circulate.

Going to court

Davis had saved a milk-jug of the gas taken from his vehicle with a notation from his mechanic. But a small claims court ruled in favor of Kroger because Davis's gas sample did not get properly tested by a third party, and also because it did not satisfy the standards of "chain of evidence." Water, in theory, could have been added to the milk-jug. Without the state inspector on Davis's side, it was going to be a tough battle.

The chances of getting bad gas in your car are small, but it does happen. The most likely time it could happen is when the tank at the gas station is near empty. Why? Gasoline is lighter than water. If there is water in the station's tank, it will be collected at the bottom of the tank.

The only thing Davis could have done differently was have his gas tested at a third party lab after it was given to him. That would cost around $300 at most labs. And even then, an opposing lawyer could charge that the gas was not taken from the Kroger pump.

There isn't much to do to guard against this problem. But one thing experts agree on is this--it's better not to fill up from a pump that is attached to a tank that is being filled up by a tanker truck. That was the case when Davis fueled up at the Kroger. It is at this moment that the tank is low, exposing possible water, and also the time that water, if it's in the tank, is sloshing around with the gas before it settles.