The OP is trying to do the right thing here. I estimated my mileage for the purpose of filling up from incomplete fillups early in my ownership of the Sahara and ended up running out of fuel on I-10. My issue was the vent line was gummed up and not venting correctly, however even after clearing the vent, I cannot fill up using fast fill on the truck lanes. I guesstimate how much fuel I need and if I get within 5 gallons of that number I'm happy. Plus, now that I know that when the gauge reads 1/4 it's really empty, it all works out.