I have an 06 and filled it up with 87 since premium is now 4.65 per gallon in SF BayArea . Noticeable difference in power loss. Sluggish throttle response.
Going back to Premium. My VVTi does not like Regular
goddam 4.65.... currently here at east bay prices are hovering $3.56... ive been filling up 87 for a few months now and i have no ill effect... i keep below 3k RPM anyways usually letting it shift around 2k... moving 33"s + lift + sliders averages me around 14 mpg city.