I noticed you were talking about better mileage using the 89, I have the 4 cyc using the lesser octane getting about 28 on average.
Do you think stepping up in octane will improve the mileage?
I do only have 1100 miles on the car.
Do some research beyond just listening to me or anyone else.
In the manual for my V6 it says I can use 87, or for improved performance 89. On my '09 V6 I tried different octanes and calculated that premium (or high test, ethel, etc.) doesn't give better performance (butt dyno) or better mileage. So I saved the money and went back to using 89. I could tell a slight performance decrease with 87 (again, butt dyno) and a slight MPG decrease.
With my '11 V6 I just use the same pattern of thinking and use only 89.
For your I4, read the manual and see what it says.
Also, as you put a few more miles on you'll probably get the whole drivetrain worn in to your driving style so that it "settles into" your normal speed. I've driven cars that would run better at 70 than 60 due to previous owners running them for many miles at that speed. The gears set up a wear pattern that is unique to the speed and just run so much smoother than at other speeds. Has to do with harmonics and vibrations and such.
. It is rough on the roads there pretty much all the way. The factory Goodyear tires aren't the best for comfort in any condition though.
