General Motors says an offer of shares to the public could raise $US18 billion - $US5 billion more than first hoped.
Investor interest in the sale means demand has rocketed and increased the price the company can charge.
The company is currently more than 60% owned by the US government which is keen to return it to the market.
GM plans to sell 365 million common shares for up to 18% more than first estimated at a price of $US33 each.
It will also now offer $US4 billion in preferred stock - four times the original value planned.
Preferred stock carries different rights and will help to repay the company's pension debt - one of the concerns of potential investors in the share sale.