It is common the development of greenhouse gas (GHG) emissions inventories, by private and public organizations. They are used as starting point for policy makers in their efforts on the mitigation of greenhouse gas emissions. It has already been established that vehicle emissions contain methane (CH4), whose formation is strongly dependent on the type of emission control system used. In the transportation sector, methane emission can contribute significantly to the total GHG emissions, considering the lifecycle of the fuel used. Although there are plenty of data about the regulated emission from vehicles, for greenhouse gases such data tend to be scarce. For this reason it is usual to try to establish ratios between the regulated pollutants and greenhouse gases so that the latter can be estimated from the available data of the former. The most usual way to do that is to make such estimation based on a relation between CH4 and NMVOC (non-methane volatile organic compounds). In 2006 the IPCC (International Panel on Climate Change) published a new version of the guidelines for GHG inventories. The emission ratios between CH4 and THC indicated in that document are in use nowadays to help the inventories development. The aim of this study is to make an update of that ratios, for the Brazilian situation, based on the data available from new vehicles dynamometers tests, made for the purpose of the type approval processes and also for the production control made by the vehicles manufacturers.