Toyota is alleged to have done a VW Diesel cheat too, page-9

A neighbour imported one such vehicle which is 25 years old
and less than 110,000 kms...here is a pic:



PS: There was a conflict between limiting NOX gases and optimum fuel economy/
optimum performance from diesels because in order to get the max thermal
energy out of the diesel meant higher combustion chamber temperatures
and that meant higher NOX gases which are legislatively limited.

The solution from the Zeros was to add Urea (ad blue) which is the Trademark/patent
of DEF Technologies. Rather than pay the IP and the inconvenience of selling
this add-on to customers, the "cheat" was the logical solution .

EGR is used to limit combustion chamber temperatures but that has a downside
in engine durability because it can lead to bore polishing due to carbon particles
being introduced into the cylinders via the EGR valve.