When you say things like pocket and paid by mile it makes it sound like you think youll get it as a refund.
What kind of car do you plan on using for this? If you go new your going to lose 10-20k to depreciation in a year plus tires, brakes, oil changes, etc. If you go used your still going to have depreciation and maintenance plus more break downs, tow bills.. When you tell your insurance company you are driving 85,000 miles a year for business your rate is going to go way up. Granted you'll come out ahead on your taxes, its not going to be 40k ahead though.
As a sole prop my business deductions are separate from personal I file a schedule c and all that jazz to itemize business expenses. My personal is separate and I still take the standard deduction. Thats how turbo tax business has always had me do it anyway.