Tuesday is one of the cheesiest days of the year.

Sept. 18 is the made-up holiday of National Cheeseburger Day, and restaurants are celebrating with discounts and free burgers.

According to a survey by Offers.com, 25 percent of consumers chose Five Guys as their favorite cheeseburger, 21 percent of consumers chose Wendy’s and 20 percent McDonald’s. In-n-Out came in fourth with 15 percent.

More: Wendy’s offering free burgers through Sept. 30

More: Best September deals: Your guide to the month’s freebies and bargains

More: Guac fans, rejoice! Chipotle is now selling large sides of guacamole

But what kind of cheese is the best to top a burger?

The results often depend on the survey, but Livingston, New Jersey-based boutique burger chain Zinburger Wine & Burger Bar has found, based on sales, that American, cheddar and Swiss are the favorite choices. MORE