How much RustSeal would be needed to coat a standard car chassis (frame and underbody carriage)?

1 Quart of RustSeal should be enough to coat a standard car frame with 2 coats. If you want to do the entire under body carriage and frame with 2 coats, you will want to get 2 Quarts of RustSeal.

Please be sure to read the RustSeal Directions for proper prepping of your under body carriage and frame. The Frame Coater Kit is a convenient kit that gives you everything you need to prep and coat your chassis.