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Once you "go hybrid," it seems you can turn back after all.  Only 35 percent of hybrid car owners bought a hybrid again when they purchased a new vehicle in 2011, according to a report by automotive research group Polk.

But some regions of the country showed a surprisingly higher level of loyalty to hybrid cars, like West Palm Beach, Fla.,  and Phoenix, than other parts of the U.S.  Hybrid cars couple a traditional gasoline engine with a battery pack to boost mileage.

The report was based on Polk's analysis of new vehicle registrations of 75,000 hybrid owners who returned to market to purchase a new vehicle last year. The new purchases either replaced the previous hybrid or added to a household fleet.

If repurchase behavior among Toyota Prius owners isn't factored in, hybrid loyalty dropped to under 25 percent.  In March, Prius sales made up just under half of the hybrid market, Hybridcars.com reported.

Brad Smith, director, loyalty management practice at Polk, said  he expected higher loyalty among hybrid owners, but the report was not entirely surprising given the many competing options for drivers.

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

Hybrids, however, only make up only about 2.5 percent of the new car market. But, an increasing number of hybrid models are being introduced.

"There's more opportunity for owners to be loyal to the hybrid-fuel type," Smith said.

The report compared hybrid loyalty by region and found West Palm Beach had the highest level of loyalty in the country. Of hybrid car owners in that region, 43.2 percent bought another hybrid car in 2011.

Smith said he expected a higher level of loyalty in  "traditional eco-friendly markets," like California and Oregon.

"But that wasn't the case," he said. "They were no more loyal to the hybrid than the population at large."

Of note: the Western region has the lowest level of car brand loyalty in the country, Smith said.

"The West coast is a pretty fickle market," he said.

Top 15 Hybrid Segment Loyalty by Market (2011 Calendar Year End)

1. West Palm Beach, FL (43.2 percent)

2. Phoenix, AZ (40.2 percent)

3. Orlando, FL (39.9 percent)

4. Tampa, FL (39.9 percent)

5. St. Louis, MO (38.4 percent)

6. Boston, MA (38.4 percent)

7. Indianapolis, IN (37.3 percent)

8. Minneapolis, MN (36.7 percent)

9. Seattle, WA (36.2 percent)

10. Raleigh-Durham, NC (36.1 percent)

11. Milwaukee, WI (35.9 percent)

12. Washington, D.C. (35.6 percent)

13. San Diego, CA (35.4 percent)

14. Portland, OR (34.8 percent)

15. Los Angeles, CA (34.1 percent)

Overall: 35 percent