And this isn't purely anecdotal. The pricing-intelligence firm TrueCar has a team of analysts looking at historical sales data and specific transaction prices in the past (from a database of more than 300,000 vehicle sales), weighing those trends with current pricing, incentives, and market demand, to predict what will happen again over the next period, typically 30 days.
For instance, in TrueCar's last analysis of the best and worst days to buy a cars, covering February 16 through March 18, the firm predicted that February 27 would offer the highest projected discount (6.52 percent), while next Friday, March 12, will offer the lowest average discount (5.45 percent).
That's more than a $400 difference on a $40,000 vehicle.
Jesse Toprak, TrueCar's vice president for industry trends, said that these predictions start with simply looking at what happened in the past, every day of the year. "There's a very strong pattern of seasonality," Toprak said, so it's a good indication that these strong or weak days will repeat. "What's happened in the past plays a role."