GSA sets the reimbursement rate for federal employees, but that rate cannot exceed the IRS' rate. In November, the IRS announced it would increase its standard mileage reimbursement by two cents, to 34.5 cents per mile, in 2001. After performing its own cost analysis, GSA decided to echo that decision.
A number of federal travelers complained to GSA about high gas prices, but many other factors also are considered in determining the mileage reimbursement rate. In fact, the cost analysis includes depreciation of a vehicle's original cost, gasoline and oil, maintenance, accessories, parts and tires, insurance, and state and federal taxes.
Here's a historical look at the mileage allowance for use of your own car on official business: