The results come as Jeep is easily outdistancing other brands this year, with sales jumping 48.1 percent in the U.S. through May, according to the research firm Autodata. By comparison, sales for the entire auto industry are up just 4.1 percent.
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"What's extraordinary about Jeep right now is that it's outselling other brands like KIA and Volkswagen, even though those other brands have a wider variety of types of vehicles," Libby said. "Jeep doesn't sell cars, so it's effectively outselling other brands even though it is only competing in half of the market."
Earlier this year, Fiat Chrysler CEO Sergio Marchionne unveiled a five-year business plan that included a goal to sell 1.9 million Jeeps worldwide by 2018.
Because Jeep is limited to selling just SUVs and crossover utility vehicles, the brand's overall loyalty rate of 43.6 percent comes in well below Ford, which leads the industry with the highest loyalty rate of 64 percent.
"Jeep will most likely never be able to have loyalty rates as high as Ford, Chevy and Toyota because those brands have full lineups with trucks, SUVs and cars," Libby said. "For Jeep owners who decide they want a car, they have to leave the brand, so that naturally weighs on Jeep's loyalty rates."
—By CNBC's Phil LeBeau
Questions? Comments? BehindTheWheel@cnbc.com.