The scheme has been piloted with car insurance and finance brands including Budget Insurance and Warranty Direct. Both advertisers have used unique phone numbers to evaluate direct responses from the ads, which do not appear on the original web page. About 20,000 users print off car ads each day.
Auto Trader (www.autotrader.co.uk) also plans to push ads to users searching for specific car marques or models.
Martyn Hammond, sales and marketing director at Auto Trader Digital, said: "If someone prints off an ad, chances are they're serious about the car. Given that you have to have insurance, these are quality leads."