The "Copy Wage Type" tool is available in a few IMG nodes, namely in Personnel Administration and in Payroll.
You could possibly use constants from V_T511K to identify the amount to pay out, and use a Date Type from IT0041 to identify the Purchase Date of the car. In this scenario, an IT0014 with the Car Maintenance Allowance WT would be created from the Purchase Date with no amount and the number one (1) related to the unit, and a PCR would query IT0041 to identify what constant should be used to calculate the amount to pay.