Minor nitpick, but tailpipes aren't the primary source of emissions. The study is about PM2.5[0]. which will chiefly be tires and brake pads. Modern gasoline engines are relatively clean, outside of CO2, though diesel engines spit out a bunch of bad stuff.
Exactly. The noxious tailpipe emissions in a city are usually from diesel trucks, small vehicles like motorcycles (small or absent catalytic converters), modified vehicles (catalytic converter removed or diesel reprogrammed to smoke), but not modern gasoline ICE vehicles.
The love for diesel engines in many European countries was always confusing to me.
PM2.5 is also a broad category of particulates that come from many sources. The PM2.5 levels in the air depend on many sources, with wind being a major factor in changing PM2.5 levels. It’s hard to draw conclusions when a number depends on the weather and a lot of other inputs.
https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal
When you remove the cheating and give adequate weight to those emissions, diesel for passenger vehicles makes a lot less sense.
That's why before EVs started to show up on the market en masse if you walked into a dealership they would always recommend that you pick the diesel engine if you wanted to save money of fuel costs.
That was actually the reason why the Yellow vest protests started in 2018 when the French government announced that the taxation gap between diesel and regular gasoline was going to disappear gradually.
Small edit to add to the context:
By that point, when the protests started in 2018, the governments(right and left) of France and the many French automakers had been pushing diesel engines as THE solution to alleviate rising fuel costs and so justifiably, the protesters thought that someone had just pulled the rug from underneath them.
Also this measure was in direct contradiction to Macron's campaign promise which was that he was going to reduce the tax burden or at least not increase it on the middle class, especially the rural middle-class that basically cannot get a job without having a car as public transport is almost non-existent in rural France.
That and many other things which I won't get into since it is not relevant for this discussion really riled people up.
The focus has more recently shifted to reducing overall emissions of CO2 and other harmful gases and particulates, which makes diesel much less appealing.
Based on this, I've always thought of diesel as "more expensive", like you better get 15% more power/miles out of it if it's going to cost more! However, I suspect that most people purchasing diesel vehicles have as their other choice a car that would slurp premium, so for those buyers perhaps diesel is still a discount, even in Canada.
I suspect that modern (last five years) turbocharged gasoline engines are probably approaching diesel thermal efficiency, but I don't think that it's correct to say that they generally surpass it. The gasoline Ford EcoBoost is 33% thermally efficient while a BMW N47 turbo-diesel is 42% thermally efficient, as an example [2].
[1] https://afdc.energy.gov/fuels/properties [2] https://en.wikipedia.org/wiki/Brake-specific_fuel_consumptio...