I rent, so I'm a little different from an owner I guess, but I refuse to take a plane on the first take off unless it is full or at/slightly below the tabs. The totalizer in the planes I rent are super accurate, but still prone to human error if someone forgets to, or updates them incorrectly. Subsequent flights I'll rely on the totalizer, but I don't let the tanks get below 1/4 (23 gallons) planned at landing. Putting gas in is cheap insurance, saving a buck or two a gallon by flying on low tanks is not worth it IMO. The airport I fly out of is like $8 a gallon, I'm sure the people I rent from get a discount, but there are much cheaper places for gas that I fly to. In these cases, if it is not inconvenient, I'll gas up so the airplane doesn't need to fueled when I get back so the rental place/airplane owner saves some money.