When my family bought my '75 R4 in 1990 it had 195.000 kms. Add to this 250.000 kms until 1996,and another 79.000 up to today...sum 524.000 kms. Only one engine repair at around 480.000 kms due to overheating (my fault). About one year ago, I went to see a fairly good looking '72 model. When I asked the owner about mileage, he said casually "around 800.000 kms" ,without fearing that I would turn away (I admit it ran very well). We have (had...) a lot of such high-mileage R4s here in Greece, for two reasons:The climate does not allow them to rust quickly (the mechanics last infinitely) and, due to vehicle tax system, many people had an R4 as their one and only car for 20+ years (not as second or third as in many other countries),therefore most of the remaining R4s have around 300.000 kms.
But certainly the record-breaking R4s were those of the National Electricity Company and also Greek Telecommunications Organisation. They were used for network support vehicles all round the country from '69 to '97 (this means the fleet was built of '69-75 R4s, that were not being "refreshed"). They were abused by the network technicians, but maintained fairly well,and logbooked. It was not uncommon for a lot of R4s to reach the 1.500.000 kms mark, as some technicians have told me.A few "lucky" of them,that had lower mileage, are still in service today.