For many years I bought my "stuff" from my friend, who used to run his own motor factoring service, His highest quality product line was Mahle and I hold that brand in very high regard. I've noticed a number of quite recent purchases like this, although branded as always, now bear "made in China" on the packaging. Historically I would have been very worried about this and probably taken it back to swop for a British/European/American made item. However, with my local factor having been bought over by NAPA and seeing "made in China" now on not just the budget range stuff but also more premium brands, and having now used these for several years without experiencing any downside, I think we all need to accept that there's some very good stuff coming out of China now. However I think you do need to do your "due diligence" before buying. The first cars I started using this stuff on were the Ibiza and our Panda. The Ibiza? I hear you all shouting, "didn't you have a lot of problems with that car?" Well yes I did. but, it was all original equipment stuff which gave problems. The turbo wastegate failed (a known problem on the earlier turbo fitted to that engine - rectified with a modified linkage on subsequent production) The entire gearbox had to be replaced, but again due to a final drive bearing failed and yes, I did check oil level at every service and there were no lubricant leaks. Then there was the O/S driveshaft which was starting to knock when I part ex'd her. So yes, problems, in fact more problems than I've had with any car in years, but none due to items replaced at routine servicing like the Chinese made oil and air filters etc. It's a similar story with the Panda except that she's been boringly reliable with no serious mechanical failures to report and I've been using Chinese made filters etc, sometimes with the occasional German or other make depending on availability, since around '98.
Personally, if it's got a big brand name on it, and even more importantly, if it's being sold to me by a trusted supplier, I'm feeling really quite happy and confident using it. I wouldn't be surprised to find main dealer supplied and branded filters etc are actually made in some very modern and up to date factory in China somewhere? with exactly the same filters rolling down the line and being branded with aftermarket names before being put in their packaging. Of course the fact is that my factors are supplying parts to all the independents around me, many of whom I am on more than passing terms with and several who I talk with regularly. I'm sure I'd hear if there was something to worry about but also, the factors aren't going to stay in business for long if they get a name in the trade for supplying unreliable parts.
The big "Elephant in the room" here though is counterfeiting. Because, to the casual observer, some are so good you can't tell without cutting them open or subjecting them to very close scrutiny. Because of this I will only now buy from "trusted sources" which for me means much of my service and "consumable" repair parts - stuff like track rod ends, brake cylinders and calipers, timing belt kits etc, are from one of two big factors near me. I would be quite reluctant to look for this sort of thing on line except for a small number of sources I've bought from before and I feel confident with - Opie oils, Power Enhancer, Shop4parts, etc.