Honda's CR-V is one reason why crossovers and sport-utiliies are outselling sedans for the first time ever.

For the first time ever, sales of crossovers and conventional sport-utility vehicles are outselling sedans, capping a nearly three decade-long transformation of the U.S. auto market.

When the first generation of sport-utility vehicles emerged in the post-War era they were largely aimed at professionals and outdoorsmen. By the 1980s, manufacturers began targeting more mainstream buyers. But it’s only in recent years that utility vehicles have become the products of choice for millions of American families.

Industry analysts say several factors have hastened that transformation. For one thing, newer crossover-utility vehicles offer more car-like, on-road manners than traditional SUVs. A new study also points to another critical factor: the increasingly small gap in fuel economy between utes and sedans.

Not all that long ago, utility vehicles struggled to deliver even 20 miles per gallon on the highway, according to EPA ratings. Today, however, the sales-weighted average mileage is 26.83 mpg. That’s about two miles a gallon less than the 28.84 mpg average for sedans, reveals the study by data firm TrueCar.com.

A wave of new small SUVs and crossovers like the 2015 Lincoln MKC are only going to hasten the decline of sedan sales in the U.S.

“Improved fuel efficiency in top-sellers like Honda’s CR-V, Toyota RAV4, Ford Escape, Chevy Equinox and Nissan Rogue mean that car buyers see little fuel economy penalty in exchange for much greater utility,” noted a TrueCar.com statement.

The data firm noted that, on average, a compact utility vehicle owner will spend about $120 more on fuel each year than someone operating a midsize sedan – with similar interior space.

A variety of factors have helped improve ute fuel economy. For one thing, a growing number of traditional sport-utility vehicles have migrated to car-based crossover platforms, a list that includes such benchmarks as the Ford Explorer and Escape models, as well as Nissan’s latest-generation Pathfinder. The latter model shed a full 500 pounds of fuel-sucking mass as a result of that changeover.

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There’s also a whole new generation of downsized utility vehicles, such as the Honda HR-V and Chevrolet Trax, among mainstream brands, as well as the higher-end Mercedes-Benz GLA and Lincoln MKC. For many buyers, these offer more space – as well as utility – than sedans with similar footprints. That is, in part, due to more upright seating and other creative design and engineering tricks.

Weight and size aren’t the only critical factors. Manufacturers have put a lot more emphasis on improving the aerodynamics of their utility vehicles, both conventional SUVs and newer crossovers, or CUVs.

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They’ve also made numerous changes under the hood, in many cases shifting from traditional V-8 and V-6 powertrains to turbocharged four-cylinder engines – like the EcoBoost packages offered by Ford — and even hybridized powertrains such as the Pathfinder HEV.

There are other fuel-saving tricks, such as more efficient all-wheel-drive systems, some of which automatically can disconnect the driveline from one of the axles when it’s safe to operate in two-wheel-drive mode. Some utes now feature cylinder-disabling displacement-on-demand technology, as well as Stop-Start systems that shut the engine off rather than idling, say, at a stoplight.

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As recently as 2013, sedans outsold utility vehicles 36.6% of the U.S. market to 33.9%, respectively. The gap virtually vanished last year, noted IHS Automotive, and with fuel economy less and less of an advantage for sedans, “the short-term forecast point to continued momentum within the SUV/CUV segments,” Chris Hopson, manager of North American light vehicle sales forecasting for IHS, said during a recent study.