SANTA MONICA, Calif. — Edmunds.com determined that in the past few weeks approximately 100,000 car shoppers have been preparing to buy a car in the past few weeks, but none have yet to close a deal.

“There has been a recent surge of purchase intent that has not translated into sales,” Edmunds.com senior analyst David Tompkins told AutoObserver.com. “Given that these 100,000 shoppers represent about 10 percent of monthly sales, automakers and dealers should find a way to capitalize on the opportunity and entice these folks to actually buy.”

Consumers are holding onto their vehicles longer than in previous years. Edmunds.com analysts have calculated that the average mileage on trade-in vehicles is up 8 percent as compared to a year ago, and up 15 percent since January 2008. (The current average trade-in mileage is 65,883, while one year ago it was 61,038 and in January 2008 it was 57,079.)

“There is a strong correlation with the weakened economy,” notes Tompkins. “The average trade-in mileage has increased at a pace similar to national unemployment rates.”

Based on early data, Edmunds.com predicts that July sales will only be slightly higher than June’s, unless the much-anticipated “Cash for Clunkers” program generates significant activity. The program is expected to officially launch on July 24, but most in-market shoppers are unlikely to qualify. Edmunds.com lays out the specifics of the program in its Cash for Clunkers Resource Center at http://www.edmunds.com/cash-for-clunkers.