Freight transportation is a fundamental process for companies and ensures the continuity of the supply chain, but it is also the largest source of costs, representing about 60 percent of logistics costs. Given this significance, inefficiencies in the road transport mode, and the pursuit of emission reductions, the pressure to increase efficiency and reduce costs is constant in Brazilian companies. In food companies, there is also a need to control lead times and service levels to avoid compromising product quality. Thus, this work aims to contribute to freight cost reduction through the optimization of fleet sizing for the distribution of finished products, mixing between rented and third-party fleets, and considering different types of vehicles, costs, and efficiencies. For this purpose, a case study was conducted in a food company, whose factory in Rio de Janeiro serves customers throughout the state, segmented into 6 regions. The company in question has vehicle rental contracts, labor outsourcing agreements, and fixed rates for third-party freight. Using the OpenSolver add-in in MS Excel, a tool was created for optimization aiming to minimize cost, considering weekly demand for each region of the state, vehicle capacities, rental costs, labor, and third-party fleet. Different scenarios were analyzed, with higher profile constraints in the capital and general availability of contracted vehicles. As a result, there is an opportunity to reduce freight costs by 15 to 53 percent without considering regional profile constraints, just by reviewing the contracted fleet. When considering the constraints related to types of vehicles in certain areas, there is an opportunity to reduce total freight costs by 3 to 9 percent.