If you are using the rental car as your normal commute to and from work, then none of the expenses associated with your normal commute to and from work is deductible. Use the link below to see all of the rules.
Commuting expenses. You can’t deduct the costs of taking a bus, trolley, subway, or taxi, or of driving a car between your home and your main or regular place of work. These costs are personal commuting expenses. You can’t deduct commuting expenses no matter how far your home is from your regular place of work. You can’t deduct commuting expenses even if you work during the commuting trip.
Daily transportation expenses you incur while traveling from home to one or more regular places of business are generally nondeductible commuting expenses. However, there may be exceptions to this general rule. You can deduct daily transportation expenses incurred going between your residence and a temporary work station outside the metropolitan area where you live. Also, daily transportation expenses can be deducted if: (1) you have one or more regular work locations away from your residence or (2) your residence is your principal place of business and you incur expenses going between the residence and another work location in the same trade or business, regardless of whether the work is temporary or permanent and regardless of the distance.
https://www.irs.gov/publications/p463/ch04.html
