This is what I've always experienced over the years and perhaps as much as 2,000,000 miles of driving cars and trucks. Diesel engines(CARS AND TRUCKS) take much longer to break in. I know of no difinitive and reliable source for this information that is backed with any scientific evidence and I'm not about to waste my time searching for it simply because I know it to be true based on experience with driving NEWLY purchased vehicles for many years. That's all I've got to say about that.
English Bulldog Rescue
'13 X1 xDrive28i, Min. White, Sand, UP, LP, M-Sport, HK, Heated Seats, Satellite