system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do smaller vehicles not use diesel fuel?
gpt
For a long period of time Diesel was forbidden in the U.S. for new cars because it - historically - released way to much particulate matter into the air.  It wasn't worse as a greenhouse gas (global warming) but it was a disaster for air breathability - cities like LA just had to get smog out of the air.

It never really recovered from a brand perspective and when introduced with improvements the gas stations didn't have much diesel and the "pros" didn't make it worth it for the market to pick it back up.  The simplicity of the diesel engine was no longer valuable as reliability had been achieved on the more complex gasoline engines, and we had moved pas repairing small cars ourselves.  Diesel lived on in industrial settings where it was part of all sized vehicles.