Compare driving and bus travel costs.
Driving and taking the bus scale differently with party size, and that is what usually decides the answer. A car's fuel, parking and tolls are the same whether one person or four travel, so the per-head cost drops with each passenger. Bus tickets are per person, so the total rises linearly. A solo traveller almost always finds the bus cheaper; a family of four almost always finds driving cheaper, and the crossover is typically at two passengers. This compares out-of-pocket costs only — adding depreciation and wear at 15 to 25 cents a mile shifts the balance meaningfully back toward the bus.
Drive vs Bus Cost
Driving = round-trip miles / mpg x fuel price + parking and tolls; bus = ticket x 2 x travellers; driving per person = driving total / travellers
Usually two, and almost always three. Divide the round-trip driving cost by the round-trip bus fare per person to find your own crossover.
For an honest comparison, yes — 15-25 cents a mile covers tyres, servicing and depreciation. It roughly doubles the cost of driving on a long trip.