If your employer isn't giving you enough of a mileage allowance, you could be due a tax refund on your travel.

Who can claim a mileage tax refund?

Travelling to a permanent workplace every day doesn't qualify.  To claim mileage tax relief, you must: 

Not get the full mileage allowance from your employer

Travel to temporary workplaces, meaning you work at any one site for under two years.