Define the choice
Deciding whether to drive tomorrow differs from deciding whether to keep a car. Tomorrow's choice concerns expenses changed by that trip. Ownership includes bills that continue even when the vehicle stays parked. Begin with the decision available to you so that the calculation does not answer a larger or smaller question.
For the commute, record round trip distance, recent fuel consumption, the price paid for fuel and any parking or road charges. Include a regular detour when it is part of the working day, rather than assuming the shortest map route describes your journey.
Build a running cost example
An illustrative 30 kilometre round trip at 7 litres per 100 kilometres uses 2.1 litres. At $1.60 per litre, the fuel costs $3.36. Adding $5 parking makes $8.36 a day, or $150.48 across eighteen similar working days. Replace these invented inputs with your own observations.
Fuel and parking do not represent the full cost of a car. Servicing, tyres, repairs and changes in vehicle value also matter, while some ownership charges remain payable regardless of tomorrow's transport. Keep these categories separate rather than presenting the visible daily amount as an all inclusive ownership estimate.
Put alternatives on equal terms
Include the actual fare and the journey to the station when comparing public transport. If you already bought a pass, tomorrow's additional fare might be zero, but the next pass remains a future expense. Neither charging the whole pass to one journey nor treating future travel as permanently free gives a useful comparison.
For a decision about selling the car, prepare a longer comparison including ownership costs you can genuinely avoid and replacement transport for other trips. List accessibility, reliability and travel time beside the money. Those factors may justify a more expensive option. Keeping them visible helps you understand the tradeoff without forcing their value into an invented precise monetary figure.
Keep occasional exceptional journeys separate so one unusually costly day does not become the assumed price of every commute.
