Car engines run on diesel? Is this something most people ever encounter?
It never became popular in the US, although there are still a few cars there that run in diesel.
Diesel engines are typically more reliable and cheaper to run than gasoline. More low-end torque also made them easier to drive with a manual gearbox.
They never became common in the US partly because of differing emissions requirements.
They tend to have a bit better economy but an higher price, so in the end it depends on how long you keep them and the difference is not that positive in countries that tax both fuel the same, like Switzerland.
Modern gasoline engines have a few more tricks though and reduce the gap (like very high top gear, direct injection etc.).
I believe this effect is small compared to the alternative, which is that partial loads have dramatically excess air. That excess air isn't involved in the combustion, but still gets heated and pumped through the exhaust. That energy loss exceeds the pumping loss through a throttle on a part loaded engine.
Obviously the ideal case for both engine types is that you run it at a lower RPM whenever you need less power out. Unfortunately, that has other downsides (mostly slower response when you floor-it). Luckily, hybrid electric systems mitigate much of that downside by providing rapid response with electricity and allowing your engine to sit at 1000 rpm and 80% throttle in a super high gear while cruising 70mph on the freeway.
(I checked as I didn't believe it was half, but I see there's significant variation by country.)
They need less fuel than petrol, but one issue is that they don't lend themselves well to 100% city driving because this can lead to costly diesel particulate filter repairs as they clog up. Diesel cars automatically regenerate the filters (burn the muck to ash) as you drive e.g. over 40 mph for >25 minutes or so. (depends on car model) You should drive like that at least once a month.
However, where I live, longer distance driving is pretty common.
They're falling out of favor with rising diesel prices since covid and of course EV's. Companies here go full EV nowadays for several reasons, public image only one of them.
I'd also like to go electrical but seems like we're still stuck for yet a few years because they still don't offer charging poles in apartment garages very liberally, and for any kind of convenient EV use, it honestly builds upon the fact that you can charge it overnight close to home.
Edit: Actually it's more likely that I just forgot the nickname, but yeah.
Post-scandal, fewer manufacturers are selling them in the US, but there are millions sold every year worldwide in plain old passenger cars.
Source: I own a diesel car, Kia Cee’d 1.6L
It's rare enough that I often get very concerned gas station attendees warning me that I'm "accidentally" putting diesel in my car.
Have you heard about Dieselgate?
But yes "clean diesel" took off on the EU (somewhat) but in the US diesel means dirty smelly trucks/buses
So all in all, a modern diesel is pretty clean. Not as good as a modern gasoline car, but still reasonably ok and massively better than old diesels.
There is nothing inherently requiring diesel cars to be slow.