The racing sponsorships allow Kelley Blue Book and Autotrader to get in front of Cox Automotive's three most important audiences: consumers, clients and its own employees, said Stafford.
"NASCAR has avid fans that want to connect with sponsors of their favorite drivers," she said.
On the consumer side, Kelley Blue Book and Autotrader have reached more than 6 billion consumer impressions since the partnerships launch-ed in 2014.
The two sites' top social media campaigns have come from NASCAR messaging, Stafford said. Kelley Blue Book and Autotrader have seen spikes in visits to their websites or Google searches for the brands during the races.
"The breadth of the partnership is what really works for us," Stafford said. More than 90 percent of NASCAR fans say they are likely to consider a brand or service after seeing them sponsor an event or sport they follow, Stafford said, citing a Sponsorlink survey.
Kelley Blue Book and Autotrader have entertained more than 5,000 clients at races, giving them access to pit road, pit box viewing, garage tours, Q&As with race drivers and pictures at the car with drivers before the start of a race, for example. Some of Kelley Blue Book and Autotrader's dealership clients have run ticket giveaway contests for their customers.