My car's odometer is off since swapping for the taller final drive transmission from a model with different size tires.
After figuring out the difference against Google Earth, I now do what Clev does: I add something like 6.5% to the distance traveled shown on my odometer for doing fuel consumption calcs in the garage.
But I'm just being a geek. I have the ScanGauge speed/distance offset set at +6% - it doesn't do decimal places, which is why I do the math myself to get that extra 0.5% accuracy.
You'd be fine going with the calibrated SG distance.