Why would you put in a higher grade than what is called for? It does not matter how much your car costs. If the Ford GT manual told you to put in regular gas would you put in premium anyway since the car cost so much?
If your new Aveo told you to put in premium gas would you put in regular just because it is a cheap car?
I dont know what the Mercedes or the Studabaker need for gas but IIRC older camrys call for premium fuel.
