Its all stock except audio. Ill have to try that next. ive got about a lil over half a tank, and im at 140 miles.I use 89 on the versa also but it gets 360 miles.
You might want to change to 87 octane then
I had a Subaru Legacy L none turbo and 87 gave me 275 miles [it had smaller fuel tank] and when I put 89 just to see, 220 something. it was a 97 with 240,000 miles on
but if you do down grade to 87 and still can't get more than 300 miles,
then the fuel type is not the issue.
did you install a cold air intake or anything?