General Motors is extending its sales experiment on the eBay website.
The scheme, which only applies to car buyers in California, was scheduled to end on 8 September but will now run until the end of the month - despite just 50 of 16,000 cars listed selling in the first week.
But GM said the program is boosting awareness of its vehicles, with about 4000 enquiries coming via the website.
"We are very pleased with the progress of the initial promotion and its ability to raise awareness and consideration for our outstanding new-vehicle inventory," said Mark LaNeve, GM vice-president of US sales.
"The numbers on eBay itself aren't significant, but we didn't think it would be. The dealers want to continue it, and so we are working on making some tweaks to it and continue."