I have a 2.4 n/a with no tune as far as i know. I'll switch to 89 and see if i see a difference in mileage at all
I thought that there is really no such thing as 89. The storage tanks contain 87 and 93 and the pump mixes them to create 89. Or is it done at the delivery truck level, it mixes the two as it fills the 89 storage tank....89 is a slow seller at most stations,and sits longer in the tanks.Ask your station how much 89 they sale on a monthly basis.You may be getting older gas with 89.