You should really consider getting an MPGuino. It's really not hard to install, it's just 4 wires from the car that you have to tap into, and 2 of them are the basic power and ground. It really helps to see exactly what your fuel mileage is with instant response rather than waiting for a whole tank.
Either way, you're definitely doing a great job, and if you can keep that 56MPG consistent, then you're definitely doing something right.
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