The international council on clean transportation reports "the combustion of 1 liter (or litre) of diesel fuel releases approx 13% more CO2 than the same amount of gasoline (or petrol)." Diesel is also more expensive than petrol, but it has qualities which suit heavy-duty vehicle requirements better. However, an Associate Professor at the Illinois Institute of Technology has developed a computer model which, when combined with software, may be able to better manage combustion factors in working engines, so diesel engines could become "multi-fuel" engines. This could speed up adoption of lower emission fuels, without requiring large-scale capital investments.
https://www.iit.edu/news/illinois-tech-designs-new-engine-brains-could-reduce-emissions