I have a very simple metric. Can it reach it’s listed top speed? Living in Germany makes that relatively easy. Find an empty, unrestricted and flat stretch of Autobahn and floor it, have a GPS based app on your phone running to get a better idea of what speed you are actually doing. If it can reach or do more than what it should do, pretty much all the horses should be still in the barn, compression should be o.k.-ish, and so on.
My Honda did well in that compartment. Indicating that there was nothing fundamentally wrong with the eingine.
I was a little disappointed when the E61 didn’t fully deliver. Listed top speed is 241kph and on flat ground it didn’t really go past 230. Carbon build up from the one previous owner driving like an undertaker? Maybe a full service could do the trick? Well, as you might remember a little later the CEL came on and I now have a new coil for Bavarian boy number six (along with a spark plug aaaaaaand and injector),
This weekend, I had to attend a family function at the other end of a very empty stretch of Autobahn. 240+ kph on flat ground all day long!!!! So My guess is that all is good for this very moment.
How do you check if your engine is still healthy?