The average fuel economy of light vehicles sold in the U.S. rose 5% over year-ago in October, the latest WardsAuto Fuel Economy Index reports, and 13.9% above the base index score set in fourth-quarter 2007.

The combined fuel economy for all LV sales in the month was 23.8 mpg (9.9 L/100 km), slightly better than the overall year-to-date rating of 23.7 mpg (9.9 L/100 km), and a 1.1 mpg (0.5 km/L) improvement on year-ago.

Superstorm Sandy, which wreaked havoc on the East Coast in the final days of the month, is estimated to have cost auto makers as many as 60,000 LV deliveries. But the geographically focused sales loss seemed to have no affect on the index overall, as the October index was nearly identical to September.

The news that the Hyundai-Kia group misreported fuel economy results for the past several model years had a much bigger impact on the index.

Though the re-statement of the South Korean auto makers’ Environmental Protection Agency’s ratings did not change the base index score of 20.9 mpg (11.2 L/100 km), it did alter the index record high, set in April, reducing it from 24.1 mpg (9.7 L/ 00 km) to 24 mpg (9.8 L/ 00 km).

The changes also dropped Hyundai and Kia out of October’s competition for the top spots on the index. Both auto makers finished in the No.1 spot earlier this year, before the EPA’s adjustment.

Toyota finished atop the recalibrated index for the 11th time in 12 months, scoring 27.5 mpg (8.6 L/100 km). Volkswagen, which took the crown from Toyota last December, finished second, with a 26.7 mpg (8.8 L/100 km), up 1.7% over year-ago.

Mazda finished No.3 in October, with its highest index rating to date of 26 mpg (9 L/100 km), reflecting a 9.1% jump from year-ago.

The lift was achieved as sales of its larger CX-7 and CX-9 cross/utility vehicles fell in favor of the new, more-efficient CX-5, while the Mazda3 small car enjoyed a year-over-year boon concurrent with a drop in deliveries of the Mazda6 midsized sedan.

Ford recorded a company-best of 23 mpg (10.2 L/ 00 km), helping the Detroit Three to earn their second-highest collective index rating to date of 21.6 mpg (10.9 L/100 km).

Asia/Pacific auto makers scored a combined 26.1 mpg (9 L/100 km), while European brands finished with a 22.8 mpg (10.3 L/100 km) rating.

CUVs were the best-selling segment in October, accounting for 23.5% of deliveries and averaging 22.1 mpg (10.6 L/100 km) per vehicle.

The small- and midsize-car segments made up 19.2% and 19.7% of light-vehicle sales, respectively, while earning 29.6 mpg (7.9 L/100 km) and 27.9 mpg (8.4 L/100 km) index ratings.

The WardsAuto FEI year-to-date rating climbed 4.9% to 23.7 mpg (9.9 L/100 km) through October, with the gap expected to grow through the end of the year.

jsousanis@wardsauto.com