Optimizing automotive LPG blend for Mexico City

Tests were conducted on three representative vehicles of Mexico City liquefied petroleum gas fleet (LPG), using different propane/butane mixtures. Exhaust emissions, individual hydrocarbon speciation and ozone forming potential was evaluated in order to establish a LPG specification for automotive use in Mexico City. Results indicated that a change in composition from 60 to 85% propane in volume had a great effect on CO and NOx emissions but only a small one on total hydrocarbons. Mixtures having 70% volume of propane with variations no greater than 4% seems to be the best value, from the point of view of reduction in pollutants.