I have a personal car lease of $500/month. I'm in outside sales and my company reimburses me via mileage (@.50/mile). Can the company instead reimburse me for my lease payments, gas, insurance etc? Let's say I use the car 75% of the for business purposes. Thanks!

A common way to handle this is to give the employee a car allowance. It would be the same amount each month regardless of that month's usage, and it is up to the employee to keep records as to business vs. personal expenses. A car allowance is taxable, but the business mileage is tax deductible.