Reducing the Incentives to Guzzle Gas Act - Amends the Internal Revenue Code to: (1) include certain heavy vehicles (with a gross vehicle weight of between 6,000 and 14,000 pounds) as passenger vehicles to which the limitations on the depreciation allowed for luxury automobiles apply; (2) exempt vehicles used in a farming business from such depreciation limitations; (3) revise the limitation amounts for the depreciation of luxury automobiles; and (4) allow the expensing of up to $30,000 of the cost of vehicles used in a farming business.