Irving Oil's reimbursement program applies primarily to New Brunswick, but also to stations in Quebec, Prince Edward Island, and Nova Scotia. (CBC)Irving Oil announced Friday it has been selling premium gasoline below specifications for more than two years.

The company said that octane levels on its premium gasoline have been lower than expected since the beginning of 2008.

Irving Oil had already been offering rebates to drivers who bought its Plus or Supreme gasoline during 2010 after it discovered a problem Aug. 13 at the Irving Oil refinery in Saint John, N.B.

That reimbursement program opened Aug. 17 and closed Friday. Around 8,000 people took advantage of it, the company said.

That refund was equivalent to just over three cents per litre purchased since Jan. 1, which saw the company pay out hundreds of thousands of dollars.

Mistake worsened over time

On Friday, Irving Oil concluded its review of the problem — a valve failure — and determined the problem had been ongoing since the beginning of 2008.

"We were able to determine that this was not an immediate failure of the valve in 2010, but a very slow, progressive failure over the last 24 months," said Mark Sherman, the refinery's general manager.

Refinery general manager Mark Sherman said the problem occurred during the loading of fuel onto trucks. (CBC)The faulty valve caused the company's regular gas to mix with the premium gas, Sherman said. The gas was made to specification, but became mixed while it was being loaded onto trucks, he said.

Sherman said the problem has been corrected.

Irving Oil will now offer reimbursement for people who bought Supreme and Plus gasoline in 2008 and 2009.

Sherman said a reimbursement fund will be established and customers will be able to visit Irving Oil's website to participate.

Claims can be made between Monday, Aug. 30, and Friday, Sept. 10.

"Following the claim period, Irving Oil will review the claims submitted and reimburse valid claims from the fund in a fair manner," an Irving Oil news release says.

Irving has more than 100 gas stations in New Brunswick and surrounding provinces.

Most of the affected sites are in New Brunswick, with "a few stations" affected in Nova Scotia, Prince Edward Island, and Quebec, the company said.

Reimbursement affects other gas companies

Irving Oil also supplies most other gas companies in the province, including Esso, PetroCanada, and Ultramar.

Irving Oil plans to work out a deal with those companies.

"With sincere apologies, we regret that this situation's happened," Sherman said. "And we just want folks to know that Irving Oil will not profit from the mistakes that we've made here, and that we will make it right with our retail and wholesale customers."

Sherman said the company is now working on physically separating the loading tracks at the refinery to make sure the problem doesn't happen again.

The discrepancy between the advertised octane and what customers bought was less in the first two years than this year, he added.