Estimate commute cost of a job.
The true cost of a commute is not fuel alone. A per-mile running cost captures fuel, tyres, servicing and the depreciation caused by the mileage, which together typically run two to three times the fuel cost by itself. Multiplying by 46 working weeks rather than 52 allows for leave and public holidays, and adding parking or tolls gives a figure worth setting against a salary difference between two jobs.
Annual commuting cost
Daily cost = one-way miles x 2 x cost per mile + parking; annual = daily cost x days per week x 46 weeks
Government mileage rates are a reasonable proxy — around 0.45 per mile in many jurisdictions for the first several thousand miles. Fuel alone is typically 0.12-0.20, so using fuel only understates the cost by a factor of two or three.
Directly, and it is often decisive. A commute costing 4,000 a year is roughly a 5,500 gross salary difference once tax is considered, which frequently exceeds the pay gap between two offers.
For a full picture, yes. An 18-mile commute four days a week is typically 5-7 hours a week unpaid, which is around 250 hours a year — six working weeks of your life that this cash figure does not capture.