It will take us two weeks beyond eternity to get better Diesel than 50PPM, it seems. MB warranty here is good for 50PPM, but we are excluded from the V8 Diesel models, for instance.
We have the various Diesel A-Class, B-Class, then also all 4/6 cylinder Diesel C, E and S-class, but no diesel V8's. The OM642 engine also serves in ML/GL/G in its various power rating specifications, all good for 50PPM.
Namibians live in a sparsely populated desert region and sometimes a farmer's nearest neighbour is some 70 or 100 miles away. They drive at insane speeds, meaning that distance + speed provides enough heat to turn soot into ash. Their fuel was labelled 500PPM but in reality, it was 120PPM. (Here in South Africa, 500PPM means what it says)
Also, the auto markets in both Botswana and Namibia are small, due to the low population density and the third world economies. Manufacturers therefore were not at risk as much as they would have been in a developed country like South Africa, or any other first world country. A DPF that would have become congested in Cape Town within a short period of time, will most likely last a lifetime out there, where heat and speed turns soot to ash and ash to dust.
Of course, many deleted their DPF's and could not care a hoot about warranty issues, unlike we South Africans. How they addressed ECU settings is not known to me. Namibians find a way around any obstacle in no time, though; they are survivors per excellence. And their cars simply have to obey.