<prompt> Human: Does anyone have a good rule of thumb for for to measure how much your car depreciates on a road trip? Im taking a personal trip about 600 miles away and deciding whether to fly or drive and rent a car. Driving would likely be much cheaper expect for the effect of adding 1200 miles to the odometer. Calculating the depreciation using the standard IRS mileage rate adds a considerable amount to the driving cost and makes flying look much better. But I think that rate includes things besides depreciation. Is anyone aware of a different rate that would just calculate depreciation, or some other way to calculate the effect on the road trip?  <response>: The IRS rate accounts for both fixed and variable costs; fixed costs make up 20 of that amount, so you should exclude those - you incur those fixed costs regardless of whether you take your car on your road trip. You can reasonably use 0.43 per mile. Note that this does not account for tolls.Consider also the other costs and benefits of flying - you will need to pay to get to the airport, via private car, hired car or public transportation, you will need to pay for transportation at your destination, you lose the flexibility to move your travel plans as needed, but you spend much less time traveling and avoid the stress and dangers of a long drive. 