By Roseanne Tellez

(CBS) – You go to buy a new car and kick the tires, take a test drive and check the sticker, assuming the information is accurate.

Now, two major car makers say that hasn’t been true for three years.

As CBS 2’s Roseanne Tellez reports, that means 900,000 car owners can expect an apology – and cash — to make up for it.

Carmakers Hyundai and Kia are promising to make it right. At Grossinger Hyundai in Lincolnwood, managers say not one customer noticed the discrepancy until news reports Friday.

The sticker on the Hyundai Elantra says 40 mpg, but the actual mileage is 38. There are similar discrepancies on 8 Hyundai models and five Kias. The difference is up to 6 mpg on the Kia Soul, according to the EPA, which brought the problem to light after a routine audit.

It was news to consumers and dealers alike.

“My first thought was how are Hyundai and Kia handling the problem? And the good thing is they’re being proactive,” Shon Jennings, general manager at Grossinger, tells Tellez. “They’ve guaranteed 100 percent reimbursement for the life of ownership for all customers on any vehicle that was affected.”

Car shopper Bob Kussy isn’t scared off.

“I’m looking at them, so who knows. But that wouldn’t dissuade me,” he says of the gas mileage discrepancy.

Owners can take their car to the dealer, where they’ll figure out the difference in the mileage you were promised, versus what you actually got, add 15 percent and give you a debit card.

For more information about the refund process, click here.