Which car takes the least maintenance in terms of cost over a 10 year period: Ford Mustang or Dodge Challenger?

Which car takes the least maintenance in terms of cost over a 10 year period: Ford Mustang or Dodge Challenger? - 1

According to Edmunds, the Mustang costs more.

2015 Ford Mustang True Cost to Own
https://www.edmunds.com/ford/mustang/2015/cost-to-own/

2015 Dodge Challenger True Cost to Own
https://www.edmunds.com/dodge/challenger/2015/cost-to-own/

So much depends on which site you use!
Ford Mustang tends to find itself on the "desired" list of cars to buy published by Consumer Reports because of its dependability and low repair rate.
But you specify maintenance and that means for a given period of time/miles all the vehicles will require the same amount of maintenance. Because the types and frequency of maintenance items are the same for almost all cars the price for that item will be the same. Provided they were done at the same shop.