You drive approx 50,000 miles a year on business?
Since you are a W-2 employee, only the amount that is in excess of 2% of AGI counts as an itemized deduction.
Once your taxable income is down to zero, though, you gain no further benefit.
Conversely, itemized deductions phaseout at high income levels. or, maybe you are subject to AMT. The triggers for those are different for HOH than for MFJ.
https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing
Also, under the new tax law, unreimbursed employee business expenses go away starting with 2018 tax returns filed in 2019. So talk to your employer.
