It all depends on my driving at the time. If I am driving several hundred miles on the interstate and know the gas stations are every xx miles then I will run the tank to maybe an 1/8 before refueling.
On the other hand, if I am driving around town in the winter I will top off the tank when it gets close to 1/4. If I know I am heading on a road trip I will top-off the tank if it is below 1/2.
2005 SL AWD, Platinum
-OEM HID conversion & HID fogs
-OEM iPod interface
-Upgraded (non-Bose) speakers - Pioneer TS-A1702C & TS-G1643R
-Muth signal mirrors
-Valley Industries hitch and wiring harness
-Aluminum fuel tank shields