It's not just the diesels that are tough. About 15 years ago where i used to work we had a good customer who had had his 16v rocco stolen but then recovered somewhat beat up . Since it had more than 250,000k on it and he wanted something new he asked us " could you see if there's any engine damage wink wink" . As by instructions of the service manager i dumped all the oil out and then started it and let it idle. 20 minutes go by and the lifters were barely noisy. Rev rev rev the crap out of it for another 20 minutes until i was fed up . The manager then told me to take some $ for the phone and drive it around for a while. I drove it for an hour in town and then a bit on the expressway, making sure i redlined it in every gear. Finally brought it back, put some fresh oil in it and gave it back to him. The customer drove it and sold a couple of months later and we would still see it around once in a while. TOUGH!