A rigidly controlled vehicle test program was conducted to assess the impact of MMT fuel additive on the operation of Low Emission Vehicles (LEVs). Two pairs of each of five vehicle models were tested over extended mileage (75,000 to 100,000 miles). Vehicles were driven on a test track using a customer-type driving cycle and emission tested at regular intervals throughout the program. One vehicle of each pair used a Clear base fuel and the other used the same base fuel with the addition of MMT at a concentration of 8.3 mg Mn/L (0.031 or 1/32 g Mn/US gal).
For the four light-duty vehicle models, seven of the eight MMT-fueled vehicles exceeded the NMOG emission certification standards; one Clear-fueled vehicle of one model exceeded the standards, but all other Clear-fueled vehicles met the standards. All four vehicles of the one medium-duty vehicle model met the certification standards, which are higher than those for light-duty vehicles. All vehicles with both fuels met CO and NOx emission certification standards.
At the end of the program (100,000 miles), NMOG, CO, NOx and CO2 emissions for the fleet were all statistically significantly higher for MMT-fueled vehicles compared to Clear-fueled vehicles. In addition, City Fuel Economy was significantly lower for MMT-fueled vehicles at all mileages above 25,000, and on-road fuel economy for the entire mileage accumulation period was 0.6 mpg (2.3%) lower for MMT-fueled vehicles compared to Clear-fueled vehicles.