Now look what's happened to the Internet.
https://en.wikipedia.org/wiki/Irv_Gordon had a Volvo with over 3.25 million miles (5.2Tm), although it's also had 3 engine rebuilds.
And the conversion is actually fairly simple. 1M km is 600k miles, so you were in the ballpark.
The problem, if you want to call it that, is purely social/cultural.