The shady used-car salesman's trick is to roll back the odometer to make a car appear newer. Honda Motor Co.'s odometers moved faster for the opposite effect.
"I never noticed anything was amiss," said Agoura Hills resident Dick Hansen, who bought a 2006 Honda Civic Hybrid last year and thought he had put 18,000 miles on it -- but may have driven only 17,600.
Hansen, a sound mixer for a TV production company, recently received a letter about a class-action lawsuit settlement agreement that might put some money in his pocket.
Notices began going out to 6 million Honda and Acura drivers after the agreement was reached four months ago, but some are only now landing in mailboxes.
Many recipients, like Hansen, had no idea the instruments in their dashboards weren't telling the truth.
In fact, many Honda odometers were awry for years, the lawsuit claimed, adding 2.5 miles to every 100 miles actually traveled -- ending customers' auto leases and service warranties too soon, in many cases costing them hundreds of dollars in excess mileage charges or repair costs.
James Holmes, the lead attorney in the suit against Honda and one of two similar complaints against Nissan Motor Co., said his team tested odometers in scores of other vehicles from most other major automakers and found none to be so far out of whack.
Although there is an industrywide allowance for small errors, most automakers' odometers "are pretty near perfect," Holmes said, and Toyota Motor Corp.'s odometers actually tend to err in favor of the customer by often showing fewer miles than they should.
Honda said the agreement could cost it at least $20 million, including at least $6 million for refunds of lease mileage overage charges and an unknown amount for refunds on repair bills that should have been covered under warranty.
There was "no nefarious intent" on the company's part, said Chris Martin, a spokesman for American Honda Motor Co. in Torrance. But he said Honda had calibrated its odometers to show, on average, more miles than the vehicles actually traveled.
Martin said Honda was following a voluntary industry standard instituted in the early 1970s that permitted a tolerance of "from minus 1% to plus 3.75%" in odometer readings -- meaning they could read anywhere from 99 miles to 103.75 miles for each 100 miles actually traveled. The guideline was changed in the 1980s to minus 4% to plus 4% but Honda continued to abide by the old standard.
The 2.5% error that Holmes' team found was "close" to the middle of the old tolerance range, Martin said.
The odometer standard, a voluntary one set by the Society of Automotive Engineers International, allows errors because odometer readings can be affected by changes in tire size and vehicle weight, over- or under-inflated tires and even vehicle speed, because centrifugal force alters the circumference of a moving tire.
Martin said that Honda did hear from some customers who complained that their odometers or other instruments didn't work as expected, "but there weren't so many that it raised any alarms internally. It wasn't until this suit was filed that we had the opportunity to look at the situation from a broader point of view than individual customer complaints."
Honda changed its calibration method Nov. 7, 2006, the day the settlement agreement was filed in U.S. District Court in Marshall, Texas.
Martin said that although no automaker could ensure that every odometer was 100% accurate, Honda was now aiming for an error of "zero" on its vehicles.
The settlement, expected to be approved during a hearing on May 30, extends the mileage for powertrain and emissions warrantees for vehicles in the class by 5% -- twice the 2.5% discovered by the plaintiffs' attorneys.
Even errors in small percentages can add up.
Take a car with a 36,000-mile warranty and a 2.5% odometer error: The instrument panel would have shown that its warranty had expired when, in fact, it had traveled just 35,100 miles.
By the same token, a Honda customer with a three-year, 36,000-mile lease and a 15-cent-a-mile penalty for excess mileage would have paid $150 for turning in a vehicle with 37,000 miles on the odometer at the termination of the lease -- $135 too much.
The Automobile Club of Southern California routinely tests odometers in reviewing new cars and trucks and in doing emissions and fuel efficiency tests at its Automotive Research Center in Diamond Bar.
"We run the vehicles for the equivalent of five miles and we get odometer readings down to three decimal places," said Steve Mazor, the club's chief automotive engineer, "and what we've found is that most odometers cluster around plus or minus 0.5% in accuracy, and that almost none are off by over 2%."
Mazor wouldn't comment on the club's findings for specific brands of vehicles.
The settlement agreement covers not only most 2002 to 2006 Honda and Acura models but all 2007 model Honda Fit subcompacts bought or leased through Nov. 7, 2006.