Vans or straight/tractors? If straight/tractors, the best I know is nastc. You pay an annual membership of $250 i believe and you have a network of truck stops that you get a significant discount. Some places even 50 cents a gallon, some less. Ta/Petro are included along with a bunch of smaller truck stops. No pilots and loves though. They have a nice app that shows you the actual prices after discount. They give you a fleet one card and at the end of the week what you spent gets taken out of your checking account.
If you have small vans there is no point in getting this since you don't buy that much fuel to make up for the annual membership. And you have to fuel out back with the big trucks.
For a small fleet of 5 sprinter vans, you might want to just consider Wright Express (Wex) fleet cards. With Wex you can fuel anywhere, not just truck stops.
With WEX fuel cards drivers can fill up anywhere and businesses can track fleet fuel expenses automatically, and save big with available discounts on fuel, tires, hotels, and more.