in the 98 Grand Cherokee 5.9 limited package, premium fuel is required. However, in 1998, the ram, the durango, and the dakota all have the 5.9 magnum engine as well, but states recommended fuel is regular. does anyone know if there are differences between these other than the computer? In an effort to make the horrific mileage of my grand a little better, first i plan on doing the 242 select trac swap, and if it was as simple as a plug and play swap, it would more than pay for itself in time to switch to a dodge ecm/pcm. has anyone done this swap, or attempted to run the 5.9 as is on 87 or 89 octane?