Gas pump good news: Cheating is down

Maybe your printed receipt is inexplicably 50 cents more than the amount on the meter, or the pump isn't giving you the whole gallon of gas you're paying for.

"The incentive is there to cheat. The only way we can control it is by doing what we do," said Carroll, chief of the Massachusetts Division of Standards, the agency responsible for inspecting gas pumps statewide. "We protect people where they can't protect themselves. They take it for granted that when they pull up to the gas pump they'll get the right amount. But there's a lot that goes into making sure they do get the right amount, and the right quality."

Carroll knows all the tricks because he's been on the job for more than 50 years, including decades in the field as a station inspector.

Back when he started, cheating was a whole lot easier because testing procedures were primitive. For example, it used to take more than a week to analyze the octane in a sample of gas. By the time a violation was found, the gas station had long since peddled away the fraudulent batch of fuel.

Nowadays infrared octane scanners can test a sample in less than 10 seconds, while the mobile laboratories state inspectors drive have measuring drums so accurately calibrated they can tell to within a tablespoon whether you're getting a full gallon or not.

With better technology, thievery has virtually been eliminated.

"It's been five or six years since we've had a violation in the state," Carroll said.

Gas stations have been subject to annual inspections since Massachusetts passed the Motor Fuel Sales Act of 1939. Communities with more than 5,000 residents inspect their hometown gas pumps; the state inspects the rest, including stations on major highways.

Because the state has more sophisticated equipment than most communities - the infrared scanners, which fit in briefcases, cost $10,000 each - more than 50 cities and towns also hire Carroll's department on contract to inspect their pumps. One of those communities is Wilmington, where I recently met Carroll and field inspector Martin McHardy for a firsthand primer on testing a pump.

The two men already had set up their portable laboratory - a wagon filled with shiny equipment pulled by a pickup truck - by the time I arrived at the small, Route 62 Citgo station. For each pump, McHardy made sure the gas was correctly priced, the nozzle dispensed accurate amounts of fuel, and the octane matched what was posted.

To write up a station for an octane violation, Carroll said, a reading must be more than a whole point below what's posted on the pump.

"There has to be some leeway," he said.

Since all gas grades are "fungible," it's legal to mix low octane (87) and high octane (93) to get mid-grade gas (89). In fact, many stations do just that.

To my surprise, Carroll told me that Massachusetts does not dictate what grades of octane gas retailers must sell. Were our state mountainous like Colorado, he said, we'd see stations selling 85 octane gas because it ignites faster than higher grades. In oxygen-poor air, that's an advantage.

As for scams and potential pump errors, Carroll told me plenty. Does the cash meter return to zero after each purchase, or does it read $1 before the next customer begins pumping? Is the black hose between the pump and the nozzle filled with gasoline before you start filling up? If it isn't, you could end up paying for a half a gallon that never makes it to your car.

"There was a scam in LA where they put a smart chip in the system. They know [inspectors] test 5 gallons at a time, so the pump was accurate at 5 gallons, but every measure below or above 5 gallons was inaccurate," Carroll said.

In the end, our Citgo station passed every test, so McHardy affixed a red Division of Standards sticker with his signature on each pump, then returned all the fuel he had tested to the station's underground tanks.

Now that spring is here, he'll inspect 10 or more stations a week until his list is complete. Though if history holds, McHardy said, most drivers will never notice.

"I had a woman the other day say to me, 'Wow, you do exist. I see your name all over town.' "

Peter DeMarco can be reached at demarco@globe.com.