Using a bit of diesel fuel to ignite natural gas in an engine is one way to provide high-power output with lowered emissions. Clean Air Power, which has a unique retro-fit system that gives an engine dual-fuel capability, recently completed trials meant to figure out the benefits of integrating versus retro-fitting its products, and discovered that the cost and CO2 emissions savings are better with the contemporary integrated system. Clean Air Power says that the UK trials, which used the Genesis Dual-Fuel[TM] retro-fit system, demonstrated a 50 percent gas substitution and a CO2 saving of 8.4 tons a year, based on 200,000km annual mileage. The lowered gas usage could save operators about $12,000 per vehicle per year in fuel costs (thanks for link autobloggreen com ;-)