The idea was that "clean diesel" emitted slightly less CO2 than the average gas powered vehicle. However, after the mass rush to buy diesel engines, it soon came out that not only were those reductions in CO2 somewhat overstated, but that diesel produced substantially more fine particulates, which strongly impacted urban air quality.
Wonder what the back story is there. Car companies sponsoring scientists to make certain findings.Science is often corrupted by human agendas.
It was thought that diesel was cleaner way back in like the 80s. Another factor was regular gas still had lead, and diesel was for sure cleaner than leaded gas. That's why companies like Volkswagen went heavy into diesel cars back then, virtually all of their cars were diesel then. But as time goes on, science gets more tech, and learn more things.Also, diesel back then was like half the price of regular gas.
I remember maybe 15 years or so back Korean car makers were selling LPG-powered minivans, but I guess that never truly caught on. The taxis run on LPG, which makes their trunks quite small.