Big vehicles kick off 2015 with big gains

The powerful combination of cheap gas prices and strengthening consumer confidence are driving Americans to buy trucks, SUVs and crossovers at their fastest pace in years.

In some cases, sales of these vehicles are running at record rates.

"There's no question about it. The price of gasoline determines the type of vehicle customers buy," said Mike Jackson, CEO of AutoNation, the country's largest auto dealership chain. "They determine that on the price of gasoline at the moment they buy, not what they think the price is going to be [in the future]."

2015 Jeep Cherokee
Source: Chrysler

AutoNation on Tuesday reported much stronger-than-expected earnings for the fourth quarter, largely because of a surge in auto sales during the holiday season. The sector's strength carried through into January sales reports from the Big Three automakers, which have long dominated the larger-vehicle segments.

Read MoreAuto sales on pace for a big year: AutoNation CEO

Sales of those companies' trucks, SUVs and crossovers were particularly noteworthy during the month.

At Jeep, for example, sales popped 23 percent, as the Fiat Chrysler-owned brand reported its best January ever. Leading the way was the compact Jeep Cherokee SUV, which grew sales by 44 percent compared to the prior year.

General Motors' truck sales climbed a whopping 42 percent during the month, thanks to strong demand for the Silverado and the new mid-size Colorado pickup.

Read MoreGlobal auto sales remain on uptrend: IHS

The Ford F-series had its best January since 2004. Even more impressive was that buyers were willing to pay more for the new truck, as the average transaction price climbed $2,100 year-over-year.

Best Q4 ever: AutoNation CEO
Best Q4 ever: AutoNation CEO

"We certainly do see a favorable impact [from] low gas prices," said Emily Kolinski Morris, chief economist for Ford Motor.

Not surprisingly, small cars are likewise stirring up smaller interest with American consumers. Ford estimates the percentage of small cars sold by the auto industry in January fell one percentage point to 19 percent, as compared with sales of one year ago. By comparison, industry estimates say trucks (including SUVs and crossovers) account for an estimated 55 percent of all vehicles sold in the U.S.

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Both the range-extended electric Chevy Volt and the all-electric Nissan LEAF had slower sales in January. GM sold just 542 Volts last month, a decline of 41 percent compared with sales in the same month last year; Nissan sold 1,070 LEAF models, a drop of 17 percent. America's most popular gas-electric hybrid, the Toyota Prius, saw sales volumes come in relatively flat.

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