The IRS is giving a deduction of 40.5 cents a mile for business travel driven for 2005. This is up from 37.5 cents per mile in 2004.
While most of the time chasing cannot be considered business travel, the IRS deduction is a ballpark figure on how much chase mileage is costing you. The real cost is much, much more than just fuel.
I figure that wear and tear alone is costing me more than $135 per 1,000 miles I put on my car (~14 cents per mile), assuming my car lasts for 200,000 miles. That's just by dividing the purchase price of the car by miles driven. That doesn't count repairs, oil changes, fuel, tires, brakes, insurance, inspections, etc. The IRS figure counts in all of those items. Of course the actual number will vary depending on the type of vehicle, IE an SUV will cost more to operate per mile than a small car.
Bottom line is that budgeting for chase season often ignores the fact that you're taking a huge chunk out of the life of your car and therefore decreasing the time interval between car purchases. A 3-week chase trip might cost you $3,000 in gas and hotels, but might end up actually costing you $6000 to $7000 when you factor in vehicle wear and tear. That extra cost won't manifest itself until you have to replace your car 1 or 2 years earlier than you normally would!