The valve seats were hardened so it could run on unleaded fuel.
By contrast, the last big change, to unleaded fuel, was gradual, with only enough produced at first to supply 1974 model cars.
But after the publicity on unleaded fuel there has been increased interest in used diesel power.
I fitted catalyst, and have been running vehicle on unleaded fuel with no problems.
Built in the 1960's, it is not equipped to handle unleaded fuel.
By 2000 the great majority of cars will run on unleaded fuel.
The engine can also run on unleaded fuel without modification.
But they made the same complaints when Congress told them to develop unleaded fuel and cars that could run on it.
Engines were modified to run on unleaded fuel from January 1986.
All 2CVs from this date can run on unleaded fuel.