MPGuino showing typical numbers as of this AM:
49.9 MPG over 39.2 miles. That's in 2 days' use, about a 1/3 mix of sub/urban to 2/3 secondary highway driving in hot (25-30C) weather.
UNFORTUNATELY, my MPGuino is a bit buggy.
It randomly resets itself. That 39 mile reading is one of the longer stretches it's gone without a reset. Sometimes it resets multiple times over the course of a short trip, and sometimes (rarely) it completely freezes, requiring a hard reset (unplug).
I keep meaning to check for bad solder spots, but haven't gotten around to it yet.
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I posted a dedicated
MPGuino / Miata installation thread.