The new research, from Motors.co.uk, also shows that 8% would use these sites to actually buy a used car and 7% saying they would use it to buy a new car.
The research was conducted among 1,000 car buyers by Redshift Research in September.
The research also shows that consumers in Wales are most likely to buy a new car (15%), used car (10%) and book car servicing via group buying sites (15%).
This contrasts sharply with consumers in the East of England, who are least likely to buy a new or used car using group buying sites (3%), or use the site to book car servicing (6%).
Phill Jones, Motors.co.uk commercial director, said: "Group buying sites such as Groupon and Wowcher have been making inroads into the car market having already sold car servicing MoTs and accessories.
“We know that Groupon have experimented in the US with car purchase, but we think it is only a matter of time before a dealer or manufacturer in the UK strikes a deal that appeals to consumers."
Jones said the industry was likely to see growth in vouchers and coupons for car and related services over the next few months as consumers continue to feel the pinch.