Amazon (AMZN.US) officially launched Amazon Auto in 48 cities in the US on Tuesday, aiming to compete with Costco's (COST.US) popular car-buying program.Amazon Auto will initially offer online car shopping services from modern car dealers in major metropolitan areas across the US, according to the company. Amazon plans to add more manufacturers, brands, cities, and new features to its online car-buying program by 2025.The Amazon Auto online experience will allow users to browse and search for available vehicles at local dealerships by brand, model, trim, color, and features. Customers can also get instant valuations and trade in their existing vehicles for new ones. The program also features transparent pricing and financing options."We are working with dealers and brands to redesign car shopping to be more transparent, convenient, and customer-friendly," said Fan Jin, CEO of Amazon Auto.Costco's car program allows members to buy new cars and certified used cars. The program works with a network of over 3,000 dealerships across the US. Meanwhile, Walmart (WMT.US) also offers car-buying services, but they are less mature than Costco's. Walmart's service mainly plays a facilitator role, guiding customers to local dealerships without the structured program like Costco's.