I try not to ride mine out, but nearly always let the light come on before I put fuel in it, being that I fill up whenever I add fuel.

03' Eclipse GS, farthest I've even gotten was 32mpg witht he light on before I decided to stop and fill it up. However, come of the guys over on Club3G have claimed getting low 40's before running their tanks dry.

On the Imark, the fuel gauge is crap so I really couldn't tell you. But I was getting 30+mpg so it really dosen't matter.