Mileage Allowance for Directors

Looking for some guidance on how to record a mileage allowance payment through quickbooks.

There are two directors who pay themselves a salary.

They will both be claiming the mileage allowance. When paying the two directors their mileage allowance will this simply be treated as an expense and therefore recorded as a debit in a 'petrol' account? Or do I have to go through a directors loan account? 

Any help would be appreciated.