Miles Vs Actual Expenses

[jefffieldstarz20]

Uber/Lyft
I'd like to deduct Actual Expenses (gas, car wash, maintenance).  Why is Turbo Tax still asking me for total mileage?

[Phillip1]

The deductible portion of automobile expenses is determined by calculating a percentage of business usage for the year. The business use percentage is calculated by dividing business mileage by total mileage. TurboTax requires the total miles driven and your business miles in order to calculate the correct business use percentage.

[jklmbenck]

Do I enter the full auto expenses and does TT then compute the business percentage from the usage I included?  Or do I need to enter expenses based on the % business use computed by TT?