Jupiterimages/Thinkstock(BALTIMORE) -- The average price of a gallon of gasoline now stands at $3.96 a gallon, according to the latest Department of Energy numbers, so imagine not getting what you pay for. ABC News went along with Maryland inspectors as they conducted surprise inspections at the pump.



First and foremost, the Maryland comptroller's office tests to see if the gasoline is the correct octane level. Inspectors also look for contaminants, like diesel, sediment and water in the gas. Much of the fuel these days is a blend of gasoline and ethanol and if even a few drops of water get into it, it will separate. If you put that in your car, it will stall and could even ruin the engine.



The first station the inspector visits passes on all accounts. The second is a different story. The premium sample from the pump isn't 93 octane like it should be. So the inspector draws a sample straight from the underground tank. It fails, too.



Maryland's state of the art fuel testing laboratory provides the official verdict. "It is a fail," Mark Brandenburg of the Maryland Comptroller's Office said. The pricey premium gas that's supposed to be 93 octane is actually only 90.5 octane.



"When the economy is as bad as it is, see the gas prices rising, the food prices rising, everyone is very sensitive to whether they are getting a short end of the stick," Peter Franchot, comptroller of Maryland, told ABC News.



In this particular case, the inspector returned to the station and ordered it to stop selling premium. The station blamed the supplier.



The Maryland Comptroller's Office has one of the most aggressive fuel-testing programs in the country.



Only 40 of the 50 states perform surprise inspections. Here are the 10 states that do not yet have a program in place to test the octane level and purity of gasoline:

Hawaii

Alaska

Idaho

Illinois

Kentucky

New Jersey

Oregon

Rhode Island

Vermont

West Virginia

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