Prestons BMW in Colne, Lancs, reports that its website is now responsible for generating around 20% of its used car sales.
Lee Collins, Prestons BMW managing director, claimed the business - as many as 12 units a month - was in addition to trade produced from showroom traffic.
"We have an internet response team that deals with all website enquiries - analysis has revealed that they are dealing with around 20% of our used car sales volume," he said.
He believes the internet is an ideal medium for used cars. "It applies more for used than new because each car is unique, in terms of mileage, colour and condition. "We won't sacrifice our traditional means of retailing, but the internet has offered an opportunity to deal with a new audience."
Prestons' website - www.prestons.co.uk - is the third incarnation of a site launched two years ago.
Designed by company-owned Motor Industry Web Services, which offers its services to other dealerships, the website was heavily advertised in local media and is promoted on all Prestons' stationery.
"Our telesales people actively refer customers to the website to review the car before they visit the dealership," added Mr Collins.
Mark Powell, Prestons sales manager, said: "The main attraction of shopping for cars on the net is the convenience factor. Shoppers can browse at their leisure, secure the car of their choice with a credit card deposit and have it delivered by transporter within 48 hours."
The website has enabled Prestons to widen its catchment area, taking sales outside the North-west territory, including London.
"The fact that one-fifth of our used car sales are conducted on the internet shows that the web has revolutionised the way customers shop," said Mr Powell.
Prestons is developing a "kids' website and club" intended for launch in January. Mr Collins said the aim was to get children involved within the dealership, building loyalty for the future, when they become car buyers.
"We will also have events for kids which will improve our association with the local community," he added.