We've been traveling with our Euro 4 truck's in North Afrika ( Morocco , Tunisia ,Libya ) and eastern Europe and also with Euro 4 CRD Wrangler Jeep's. Due to the higher amount of sulfur the exhaust tip became green , but no dammage to the DPF filters and sensors. As the DPF get's realy hot it burns the sulfur.
The most important is good filtration to avoid water in the common rail.
Ad blue is another problem , in my former Iveco or my friends Mog U400, we had some extra jerry cans with ad blue to cover the trip , but in Euro 4 the truck still runs without ad blue , it only give's an error code on the dashboard.
End this year with Euro 5 , the truck has to shut down engine power once started without ad blue ( but while running it's not allowed due to safety).
Renault Truck's did two expeditions with Euro 4 Kerax trucks , they did the Silk road , and last year they did Cape to Cape Overland. They had also extra ad blue tanks in the truck and filled up in Ankara ( turkey ) to cover the whole African trip with the ad blue they stocked.
And yes it's a real issue about witch you can discuss for hours , but if we Europeans want to buy a NEW truck , get it on the road legally here in Europe , we have no choice.( same if we want to buy a new 4X4 )
And honestly over the years that we are travelling ,we've seen the quality of the gas station getting better year by year , and also the quality of the cars in those country's.
And with the big issue about global warming I think it will even go faster than most off us think