Premium blended gasolines have all the necessary additives in them. Nothing else is needed, buy good fuel that's it. The ECM is programmed for fuels where car is sold.

Sunoco had the highest flash point, followed closely by Shell.

As you may not know, Sunoco is fuel of NASCAR and NHRA as it has the highest octane level short of aircraft fuel which many 70's Muscle Cars run on (unless you can get Octane Booster cheap) while Shell supplies F1 Ferrari. Unfortunately we cannot get Elf or Petronas in North America.

Happy motoring