Cornish_Blue, have you ever heard of an issue with the M270's with 'Wrist Pins' where excess play in the piston connecting rods give out this kinda rattling/ticking sound? apparently it affected a certain batch of engines assembled at a Nissan plant. Or something.
It seems to be something the 'Merry Cans' experienced around 2016 ish but I've not been able to verify if any of our Q30's were affected; I e-mailed Infiniti Europe but didn't get an answer.
Reason I asked was mine makes an light 'ticky' sound but I have deduced this to be a common feature with Direct Injection Petrol Engines these days, it's certainly nothing of concern to me anyway.
This is very subjective... You could be correct about the small end piston wrist pins, manufacturers are always monitoring failures, it's all a balance of failures vs costs as I am sure you know. You will be lucky to get anything out of Infiniti corporate, best ask the Nissan / infiniti techs about any technical service bulletins relating to engine issues.
You probably get a balanced response from an independent MB garage. These engines are quite old now so any issues should have been ironed out a long time ago. If you reflect on how many MB cars have these engines I guess it runs in the 100s of 1000s if not more... Some cars are a lot heavier too like the C class E class etc so the stress on the powertrain would be greater, leading to more failures, it is lack of servicing or inferior products is a far bigger issue I think.
As I understand it MB made these engines in Germany and shipped them to the UK for our Q30 cars, so quality assurance should be as good as it gets. These engines were machine made and human handled really. I read a MB document stating these cars were designed for at least 150k miles with standard servicing. If you upped the servicing then maybe add another 100k. The internet doesn't help either, it's a bit polarised - meaning, what every you want to research, good or bad, someone somewhere has nailed the answer you are looking for 🙃
Engines are built with thinner components so make more sound, injectors, fuel pumps, VVT units all make noises. Easiest way to tell if you have a good engine is monitor its oil consumption, MPG and see how clean it is internally. Our cars are light weight, not the sort of vehicle a buyer would 'rag' about in etc. I normally say it's far more likely that a car will corrode and fall to bits rather than having the powertrain wear out if its been maintained correctly. As some people say, just drive it and enjoy it. I know I do 🙂🙏