[SpeedRye]

15mpg City Driving
15mpg Highway
I seem to get 15mpg no matter where I go or how I drive.

Pretty much the same here. Off-road, on-road, back roads, in town, on the highway. The only time I typically get lower gas mileage is on the highway at higher speeds. My 35s on stock gears like running 90mph in 6th gear. Seems happiest there, despite the protest from the falling gas needle.

 

[SpeedRye]

What engine RPM are you seeing with 35's at 90?

Excellent question, I have no idea and don't drive too much on the highway. I'd guess in the 2600-2700rpm range off the top of my head.

 

[SpeedRye]

What engine RPM are you seeing with 35's at 90?

Had to run to a job site today. 2725-2750 rpm at 90mph.

 

[SpeedRye]

I have kept track of miles per gallon (MPG) my last 14 tanks of gas - similar to you I put 15ish gallons in each fill up. I always run 87 from Sam's Club unless otherwise noted below. My FJ is basically 100% stock, 2012 with Convenience package and Off-road package, 110k miles.

19.86
17.78
19.44
19.15
18.18
19.79
16.57 (camping trip - more off-roading)
19.49
19.76
20.38
16.79 (Costco gas)
17.67
18.97
19.26

Automatic I assume?