Originally Posted by JCL

The OBC is not expected to be accurate with this box installed. It is a documented side-effect of the box fooling the ECU. If you are measuring from tank to tank, and calculating manually, I would be interested in any improved fuel consumption. Unlikely though, as it takes fuel to make power, and if you are noticing more power, you are burning more fuel. If you aren't using any of the increased power, you wouldn't burn more fuel, but then what would be the point of having the tune?