Not in my experience in both SR5's and the Cross8 and the CV8. You may get better on 95 or 98 but it is lots dearer and you lose the benefit. These engines retard the timing on 91 and they start to lose economy. E10 is about 95 rating. The Cross8 was tuned for 95 and was happy with E10, pinged its tits off on 91. Got similar economy and power on E10 or 95. Hilux seems to like E10, bugger all difference to 95 or 98, maybe 0.5L/100 max difference