Autogas is very much cleaner when compared with diesel. With respect to Nitrogen dioxide (NO2) the emissions from Autogas are only around 8% of the emissions from a diesel engine vehicle.
Recent studies have shown that particlulates contribute toward the death of up to 10,000 people every year in the UK. This is now the most harmful exhaust emission and has only been subject to legislation since 1993. The emissions with Autogas are only 6% of those produced by diesel engine vehicles. These particlulates are visible on a hazy sunny day. It is these very small particles that cause the haze.
The emission comparisons relative to petrol are that: Autogas emits significantly
less carbon monoxide (C0) and hydrocarbons (HG). When compared to diesel
Autogas emits significantly less N0x and particulate emissions are almost
eliminated.