Fuel Economy - What do you get out of a tank? (3rd gens only)

[Dave]

I don't bother putting premium in my tank anymore! Makes absolutely NO difference to consumption what so ever. The 3rd gens are tuned to run on 91, anything higher than that is useless for trying to save money.. OK My 2002 TJ executive 3.5litre Auto.. an easy 730km per tank. My current 1999 Verada 3.5 litre Verada, 550km on a bad week of me thrashing it or 600 or so on a week of driving 'nicely'

I get better distance from premium and car runs smoother to boot. Yes, there is no way to advance or retard knock
in a 6G74 but my car does run better on 98. It also has more additives to assist the engine in burning off carbon/soot deposits