I have a 2014 Nissan Altima. It gets better gas mileage than any vehicle I've ever driven, other than motorcycles. On long highway/interstate trips, I get 550-6

I have a 2014 Nissan Altima. It gets better gas mileage than any vehicle I've ever driven, other than motorcycles. On long highway/interstate trips, I get 550-600 miles on a tank of gas (the tank holds about 12 or 13 gallons, if memory serves). My girlfriend has been driving it for the last year or so and the only times I drive it anymore is to take it in for an oil change or maintenance, but I often check the statistics and it averages 34 mpg overall (most of her driving is highway). The "low fuel" indicator in it also comes on with somewhere around 100 miles remaining. I did drive it far enough once without stopping for gas that the "miles left" indicator read "---". I was about 10 minutes from home and figured I'd chance it (there's a gas station at the intersection where I turn off the highway to come home). My thought was that if I had designed the "countdown indicator", I would be in a bit of a buffer so that the car doesn't actually die going down the road when it hits zero, so I was certain I still had enough gas left to make it. My truck (large 2013 Dodge Ram) averages right about half of that. Its "low fuel" indicator comes on with about 50 miles remaining. The Harley gets around 50 mpg (and offers to find the nearest gas stations when there is ~35 miles remaining).