A first-quarter surge in small-car deliveries lifted the average fuel economy of new light vehicles in the U.S. to a non-Clunker high, as gas prices rose rapidly and several recently launched high-mileage models began to hit their sales stride.

Fuel economy for vehicles sold in the year’s first three months rose to 22.7 mpg (10.4 L/100 km) and came within a few hundredths of a point of the record set in the Cash-for-Clunkers-influenced third quarter of 2009.

The performance represents a 1.9% increase over like-2010 and a dramatic 2.8% jump from last year’s final quarter, when deliveries of larger vehicles were trending up against the backdrop of an improving economy and stable fuel costs.

However, gasoline prices, which had risen about $0.25 a gallon between January and December 2010, rocketed some $0.56 a gallon on average over the first three months of 2011, raising the specter of the 2008 spike that lifted pump prices above $4.00 a gallon and caused a temporary shift in consumer car-buying habits.

Related document: Ward’s Fuel Economy Index

Small cars accounted for 19.4% of all sales in the first quarter, the segment’s largest share since Cash-for-Clunkers, and nearly three share points more than in the final period of 2010.

In addition to overall concerns about fuel economy and cost, the segment was helped by the ramping up of sales for the new Chevy Cruze, Hyundai Elantra and Volkswagen Jetta.

On the other end of the spectrum, light trucks accounted for 50.6% of deliveries for the period, up slightly from year-ago due to ongoing gains in the Ward’s Cross/Utility segment, but down considerably from the 54.6% of the market made up by light trucks in the final quarter of 2010.

The quarter to quarter drop in light-truck share is a seasonal trend, but was amplified by consumer fears of high fuel costs and a shrinking reliance industry-wide on the truck-heavy commercial sector to drive the market as retail demand escalates.

Domestic LVs vehicles earned a 21.8 rating on the Ward’s Fuel Economy Index, up 1.3% over year-ago, with cars scoring 25.2 against a light-truck rating of 18.8.

Imported LVs jumped 3.5% over year ago to a 25.5 rating for the quarter, with cars at 27.6 and light trucks at 22.2, according to the Ward’s Fuel Economy Index.

Toyota continued to lead the index with a 26.2 rating, followed by Kia at 25.1. Jaguar Land Rover earned an industry low 15.2 rating, a 1.8% decline from year-ago.