I have the opportunity to have my employer provide a stipend for using a personal vehicle for work.  It will probably be a 60% work, 40% personal use ratio. What does that do to me tax-wise?

I assume that it wipes the "tax-relief" away and I get hit with the full percentage ($5/100 in my county).  Is that correct?

Just asking so I can accurately negotiate the stipend.

As you saw, here is the rule:

f you can answer YES to any of the following questions, your motor vehicle is considered by State Law to have a business use and does not qualify for Car Tax Relief.

   Is more than 50% of the mileage for the year used as a business expense for Federal Income Tax purposes OR reimbursed by an employer?

Drive more personal miles/less business miles so that it's less then 50%?

As oppose to a stipend based on usage, can they reimburse you mileage or say that it's a flat $500 month, lease you a car?

Thanks! 

It's going to be a flat rate.  I am just trying to determine what would be reasonable based on how much I would use the car vs what my employer should pay for and how the PP tax fits in.