You will have to track your maintenance the old fashion way, just write it down or use an excel spread sheet as a conversion chart of sorts.
(Mileage on Odo) - (estimated on engine) = baseline difference.
Use excel to constantly track and automatically subtract the (baseline difference)...and you'll be able to easily track "actual" mileage.
2001 SP1 (sold)
2004 SP2 (properly stored)
2012 Ruckus (stolen)
2015 Grom (under construction)
Weyrauch pronounced (Y Rock)...Rock for short.