TIO report today says that newer vehicles on road are polluting more than the older vehicles !
"new cars in India are spewing more greenhouse gasses than older models,
pushing up emissions in Delhi alone by 72% in five years (2002-07), the Centre for Science and Environment said on Monday, releasing
its analysis of emissions data accessed from the Automotive Research Association of India."
One reason they mention is that size/power of vehicles in increasing and hence the reduction in mileage..fair enough.