Looking to replace your car with a newer model of the same make? Watch out. Your loyalty may actually cost you several thousand dollars more for the same car than a person who is switching his or her allegiance to a car manufacturer, said Dick Wittink, professor of marketing at Cornell University's Johnson Graduate School of Management, and co-author of a new study on the relationship between brand loyalty and automobile prices.

"Loyal customers pay a premium to stay with their desired brands relative to what other consumers pay to get the same car, " Wittink said. "This is good news for automobile manufacturers trying to cultivate brand loyalty. But for consumers, it means that the loyal customers are subsidizing those who switch allegiance."

Wittink and his colleague Rahul Guha, an associate at Cornerstone Research in Cambridge, Mass., analyzed data from a survey of 3,000 new car buyers conducted by Newsweek in 1988. They found that loyal Buick customers paid $1,051 more on average than customers who switched from another make to Buick. Loyal Eagle customers paid $1,615 more than "switchers," and loyal Nissan customers paid $2,280 more.

For luxury cars, the difference was even greater. Porsche loyalists paid $4,782 more on average than those who switched to a Porsche; Mercedes loyalists paid an extra $7,410.

"Part of the reason for the higher price is that those loyal to a particular brand usually spend less time searching for a new car than those who are switching carmakers," Wittink said. "They visit fewer dealers, are less likely to consider alternatives, and may do less research."

But Wittink also offered another reason for the gap -- based on the dynamics of the bargaining process itself.

"By driving into a Mazda dealership in your Mazda you are signalling your brand loyalty," Wittink said. "Based on this signal, the salesperson may take a harder line in the bargaining process. At the same time, the loyal customer may be less aggressive in bargaining for a better price."

Wittink's advice for brand loyalists: "Don't advertise your loyalty. Keep the identity of your current car from the salesperson until the price negotiation is complete. Give the impression that you will compare prices, and do some research."