Hyundai, Kia admit exaggerated mileage claims, will compensate owners [UPDATE] also has a table of the old and new numbers.
Interesting that they are talking about Hyundai/Kia compensating the original owners for the gas from the MPG difference, but ignoring the devaluation it brings to the car itself. How much will that knock off the resale sticker? With respect to the 230 for the volt.. it was based on a process using a procure proposed by Argonne labs to the EPA and which looked like it was going to be approved. In the end, it was not. You can read more here and here. GM was too aggressing in its announcement, since EPA had not finalized its proceedures, but it was applying the proposed formula in reasonably good faith and it was only 3 month before product was to ship. Their announcement probably resulted in the formula being changed. If nothing else it lead to an interesting discussion in the media. Real world data since then, both the data at fueleconomey.gov and voltstats (where median is 179MPG, and 1/3 of the drivers exceed 230MPG, has shown the original Argonne/EPA formula while maybe a little optimistic but not that bad.
And that would illegal in the US, so we know GM must not have meant that as a gas mileage, right? GM Volt's 230 Miles Per Gallon: New Measure Needed? - TIME Minor GM officials like the CEO and the Global Vehicle Line Executive for the Volt made that gas mileage claim.
Taken from another thread: Hyundai, Kia Mileage Mishap: How It Happened - KickingTires. Hyundai, Kia to Pay 900,000 Owners for Bad MPG Estimates - KickingTires also had some useful info.
