I can't say how often I fill up because it varies, my work has me on the road in all kinds of driving conditions, some highway, city, mountain, etc. I check my average MPG before each fill up and several times on each tank. Mine averages (according to the computer) anywhere between 33.8 and 36.7, but never less than 33.8 with the last 4 tankfulls. My first couple tanks were as low as 27.7 and has gone up pretty steadily since then. I just went out and looked at what is say's now and it shows 34.6. I for one can't complain about my mileage. It's well above what Nissan said it should be so I'm a happy camper. I normally drive at least the posted speed limit up to about 10 MPH over, and I always launch like I have to be somewhere. I've never been a light foot but so far it hasn't hurt my mileage in the cube. - Dan