I use a single vehicle for both my sch. C business and as an employee for a completely separate company in a separate industry (no connection between the sch C and employment.) I need to find some way in TT (I'm using Deluxe right now but could upgrade to another version if required) to enter the one vehicle as an asset but expense to each the sch c and unreimbursed business expenses based on mileage driven. I need to retain important data such as section 179 taken, depreciation taken and type of depreciation, mileage driven, % combined business use overall each year, etc so I can properly expense for tax purposes while at the same time making sure I'm not subject to recapture. Combined I use for well over the required 50% business use, but since there are two uses (the sch C or as an employee) one individually is bound to fall below 50% business use by itself - it's only logical - coming from a frustrated accountant:-)
The deduction for unreimbursed employee business expenses, including auto use, is not longer allowed in the Federal return in 2018, as part of the new tax laws.