The average fuel economy of new light vehicles sold in the U.S. fell slightly in 2010, as gas prices remained relatively low and recovery in the commercial-fleet sector outpaced the rest of the industry.

Fuel economy dropped 0.2% year-over-year to an average 22.2 mpg (10.6 L/100 km) rating on the sales-weighted Ward’s Fuel Economy Index.

The slight drop comes as government mandates kick in requiring auto makers to dramatically increase their corporate average fuel economy ratings over the next five years.

Related document: Ward’s Fuel Economy Index

While the average price of gas in 2010 rose to $2.84 per gallon, from $2.40 in 2009, memories of 2008’s spike to more than $4.00 per gallon seem to have faded.

Consumers turned away from the smallest vehicles in the market in 2010 in favor of cross/utility vehicles and pickups. The Ward’s Small Car segment dropped nearly two share points to just 17.8% in 2010, compared with 19.6% in the prior year. The Middle Car sector also fell, from 21.7% to 20.5%.

More than ever, consumers opted for CUVs, such as the Chevrolet Traverse, lifting the segment to its highest share to date, 24.5%, and making it the best-selling sector of 2010.

The effect on fuel economy caused by the shift in demand between these three segment groups was countered partially by an overall improvement in mileage within the segments.

Small Cars improved on the Ward’s FEI from 27.5 to 27.8. Middle Cars increased to 25.5 from 25.1, while the CUV rating rose similarly from 20.7 to 21.2.

On the other hand, commercial-fleet sales, which experienced faster year-over-year growth than the retail sector, helped boost market share for traditional light trucks (vans, SUVs and pickups) from 25.8% to 26.7%.

Also a result of commercial activity, fuel-economy ratings dropped from 17.1 to 16.4 for pickups in 2010, as mix in that sector shifted toward the higher-powered, less-efficient vehicles.

The domestic-car FEI rating rose from 24.3 to 24.6, but the increase in share for domestic light trucks (rated at 18.7) left the overall domestic LV rating even with year-ago at 21.4.

Imported LVs stayed steady with a 24.7 rating for the year, with cars at 26.6 and light trucks at 20.9, according to the Ward’s Fuel Economy Index.