tell the full story. the i-team s tisha thompson explains what to look for. reporter: think you are watching every penny at the pump these days? many, many. probably thousands. reporter: you ve got nothing on elizabeth conky. every day, she s on the road inspecting gas stations in maryland. all inspections are unannounced. reporter: for the state department of agriculture. and boy, can she stop the meter on a dime, or in this case, a penny. my greatest job skill is being able to stop exactly at five gallons. reporter: to make sure customers aren t getting shortchan shortchanged, she uses these specially calibrated containers, they look a lot like milk jugs. first, she makes each pump starts and stays on zero for 30 seconds. i pump until this says five gallons and then i read how much was actually dispensed. reporter: there is a toll perhaps. if the pump dispenses too little or too much, she can shut it down. i do find errors. reporter: theaters in keep r