A Coquitlam gas station says it's going to test its pumps after a CTV News investigation found one pump that gave us less gas than it said on the register.

Speaking through a translator, the owner of a Tempo gas station on Lougheed Highway said that an independent mechanic will come to test the pump after it came up short in CTV tests.

"I don't know what's wrong with it," said Simon Archer through his co-worker, Johnny Xu. "[The mechanic] will come in and check the pumps to see if they're okay or not okay."

As Canadians swallow one of the largest increases in gas prices ever over the weekend, they might be surprised to hear of another factor that could be pumping up the price of fuel -- inaccurate pump measurements.

The Tempo wasn't alone: government inspection records show that over the past three years, about one in ten gas stations tested across B.C. had at least one pump that failed government accuracy tests.

And according to those records, most of those who failed had errors in favour of the gas station -- meaning that on average, customers were getting less gas than they thought.

The Tempo's other pumps passed CTV tests, where CTV reporter Jon Woodward filled up a jerry can to what the pump said was 20L, and then poured it into a transparent measuring jug.

Ten other pumps at stations tested by CTV News around the Lower Mainland also passed.

There's no evidence that the Tempo was intentionally mis-measuring. The managers said the pump was past its prime, on occasion dispensing more or less gas than what was on the meter.

Records show that most errors are slight -- the equivalent of a cup of coffee per fill-up.

But some stations were found not pumping as much as two litres per a fill-up -- at today's prices, more than $3 every time you buy gas.

Even the small errors, if uncorrected, could add up to huge savings -- and profits -- for inaccurate gas stations.

Consumers should be worried, said SFU marketing professor Lindsay Meredith, as should gas stations.

"When consumers are worried about whether or not they're being shortchanged, food or gas, you'll get a real backlash," he said. "The pitchforks in the streets problem."

One motorist, Yung Hsi, says he had a bad experience at a gas station in Vancouver.

He drove until his tank was empty -- but when he filled up, the pumps told him that he was pumping more than his 50 litre gas tank would hold.

He thought he had been overcharged, and took the matter to the gas station manager, who referred him to the parent company. Hsi says he didn't get any compensation.

Since then, he's kept track of every dime he spends at a gas station. This summer, when he found a similar problem at another station, he told the gas station manger -- and the manager refunded his money.

"I think most merchants are honest," said Hsi. "They try to keep an eye on how their meters are functioning.

"But any time you go out to buy anything... you have to keep an eye on things to make sure the measuring devices are accurate," he said.

"It's very much a case of buyer beware," he said.

With a report from CTV British Columbia's Jon Woodward