Good all-terrain tires change how your truck or SUV feels on the road, giving you bite in the mud and stability in the rain. But running a premium set isn't cheap, and keeping them properly aligned and rotated adds to the total cost of ownership over the years.
If you want the best price, watch for manufacturer rebate months in April and October when brands like BFGoodrich and Michelin usually run promotions. Line those rebates up with the shop's own seasonal sales to drop the sticker price before you even talk about how to pay for them.
Remember that the zero-interest window is a hard deadline, not free money, and any leftover balance when those 15 months are up will suddenly start collecting high interest. Pay it off before the clock runs out.