To me, not being able to tell from a viewing (or listening) only is the worrying point. I was well aware of the problem before I bought our old 520d, listened for the expected rattles, etc. and only asked BMW to check it because I didn't intend to keep the car long and wanted it noted on the service invoice that it was checked and OK. The service people told me that in the test they do they measure on a scale of 1-10 and mine was 8/10, 10 not being the good end of the scale.

I'd known the car from new, knew it hadn't been abused before my ownership and had all the attention that BMW and the car said it needed and this was diagnosed with only a little over 50k miles. A colleague has one of similar age (early '11), bought as an approved used BMW and the chain snapped on his last summer. Not sure if he would be mechanically sympathetic enough to react to any tell tale increase in noises before it let go but it did it just trundling home from work one evening, leaving him on the side of the road. His AUC warranty covered him for a replacement engine but not everyone is so lucky.

For the time being I've gone back to petrol engines. HPFP's, coil packs and sundry other concerns may well exist on these but they're a more reasonable bet than a €2-3k bill for a chain replacement, if you're lucky or twice that if you're not. Goodwill from BMW, though seemingly in reasonable supply, is still a bit hit and miss. Mine was done without any arm-twisting but I think there are folks on here that haven't had the same response. There is a decent thread on this subject from around the second half of last year.

The f10 is a very fine car, pretty much outstanding as a milemuncher, but the fundamental flaw with the diesel engine would make me tread carefully on another one until history proves its been overcome.