All right, lets start some history lesson:
DAF is: van Doornes Aanhangwagen fabriek in 1932. Or Van Doornes trailer factory. later the abbreviation became van Doornes Automobile Factory when trucks and cars were added to the product line. Because of war threat and nothing available, DAF started to do 6x4 conversions on trucks that were originally 4x2 to enable them to be used as artillery tractor. the construction was very much alike a grader walking beam axle, with a single differential.
Van Doorne built its first truck in 1949, powered by Hercules gas engines or Perkins diesels. in 1956 they opened their own engine plant, using a Leyland license as a starting point, but soon their own developments progressed on this basis. The DAF 475 and 575 engines were Leyland designs, converted to Metric. They shared the same issues as any British engines: the cork gaskets that were allways sweating a bit of oil.
In 1975 the automobile division of DAF was sold to Volvo, where a DAF 77 prototype was taken into serial production as Volvo 343. In the late 80's they started building the Volvo 440 there, which was the predecessor of the S and V40 currently sold worldwide. Later on, Volvo put the Dutch factory on its own feet, keeping 50% shares, the other 50% held by Mitsubishi who produced the Carisma there, for the European market (on the same platform as Volvos V40) After Ford took over Volvo cars, Volvo production was moved to the Volvo plant in Belgium and the shares in the Dutch plant sold off.
From 1972 to 1981 International Harvester held a 33% stake in DAF, and in 1987 DAF merged with Leyland,
in the early 80 s DAF had great succes in the Paris Dakar rally, by racer Jan de Rooij who owned a large fleet of DAF trucks and also was the prime transporter of new DAF trucks to dealers throughout Europe. In those days they built the famous 615 620 and 825 engines, which are very popular in 3rd world countries because they can take more abuse than any other engine.
Jan de Rooij put the company into his son Gerards hands, but they changed their fleet to Iveco, and won 2012's dakar rally with an Iveco.
In 1993 DAF allmost went bankrupt followed by a management buy-out, but was sold in 1996 to the Paccar group. This lead to the discontinuation of the famous DAF 620 and 825 engines the same year, Paccar did not want to invest in Euro 1 emissions for the on-road market, and TIER 1 for the offroad market (DAF industrial engines were very popular marine engines, as well as used in Werklust wheel loaders) Paccar replaced them by Cummins 6BT's with a Paccar valve cover. DAF only built the 8.65 and 11.6 liter engines, which evolved into the current 9.2 liter Paccar PR and 12.9 liter Paccar MX engines.
in 1996 the US market wasnt ready for the idea of a Paccar engine in a Kenny or Pete. Also the 90's era was the era of freedom for OEMs, where you could throw in any engine, hook up a throttle cable, fuel line and battery cable and drive off, and any mechanic could work on any engine. When the engines were more and more computerised, the advantage of using Cummins or Cat because the mechanic already knew them, was vanishing because you needed a laptop to read out error codes. That meant that there was and advantage of using your own engine, serviced by your own field service technicians. So in 2010 they brought out the brand new Paccar MX13 engine in the USA. Dont know if they also sell the PR9 in Kennies and Petes.
About the DAF 620 and 825 engines, we built them into our wheel loaders at work, ever since the early days untill 1996 when they discontinued the smaller range. Nowadays many people from Africa come asking for old 16t loaders to be used in gold mines: They are becoming scarce, but they gladly take a machine with 27.000hrs if it has a DAF engine: When we dont have one and offer a post 1996 model with Cummins 6CT they smile and say no... The DAF engines could eat a handfull of desert sand and keep their compression, they just go on... a Cummins is a good engine if taken care off, but with the African service mindset, they just die early too...
So you could say that DAF (now Paccar) is africas most popular engine, which says enough about their endurance.