In the past, I have run Amsoil with great results. I have a 1999 Dodge Neon that is currently running great at 217,000 miles. It gets Amsoil every 20k and their Nano filter that states it is good to 25k. The Neon has used oil since day one to the tune of about a 1/2 quart every 5k. So the way I figure it, I get 1.5 new quarts out of 5 every oil change. No plans to ever switch oils in that car.
For the charger, since it has a lifetime warranty, I will likely be going Pennzoil Platinum or Mobil 1. Both are available locally at about the same price. I would prefer Amsoil, but not being API certified may present issues regarging warranty so I figure why take the chance. No Royal Purple anywhere to be found except online.
I also have a 2002 Turbo Diesel that has Amsoil front to back with the exception of the motor....it runs good ole Rosmella.