A surge in gas prices has helped hybrid cars and other alternative fuel vehicles capture the attention of the car-buying American public.

But not necessarily among those who have already owned a hybrid car – roughly two out of three don't buy another.

Only 35 percent of hybrid owners maintain loyalty to hybrid models when they return to buy another car, according to a survey released Tuesday authored by automotive researchers at R.L. Polk & Co.

The report was based on new registration records of 75,000 hybrid owners who purchased a new vehicle last year, one that either replaced the previous hybrid or added to their household vehicles.

Polk analysts said the percentage dropped to 25 percent when Toyota Prius owners are excluded from the data. The Prius is the most popular hybrid, selling 136,463 in 2011.

What's not clear from the data is the reason why current owners eschew a return to their hybrids. But Brad Smith, an analyst at Polk, said widening options may something to do with the admittedly surprising results.

"With diesel, plug-in electrics and hybrid cars, there are so many alternatives to gasoline," he told MSNBC.com.

AOL Autos Editor-in-Chief David Kiley offers a few other explanations contributing to the lack of loyalty. "Since hybrids first burst on the scene and began proliferating, regular gas engines have become much more fuel efficient, this giving many green-conscious drivers justifications to go back to the internal combustion engine."

Adds Kiley, "Mid-size cars are now commonly topping 30 and 35 mpg in highway driving, so paying premium prices for hybrids that get close to the same mileage doesn't make sense to some of those early hybrid buyers."

Additionally, government tax credits for hybrids have faded away, though there are still generous credits available for electric vehicles.

Read More: Automakers And Feds Pushing More Hybrids And EVs Despite Cool Consumer Response

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