I would not hold up French cars as the paragon of assembly quality. And I'm saying that as a huge Citroen fan (I've owned many different models, 2CV, DS, ID, CX, XM, C5, C8).
German cars are substantially better in quality, and finding high mileage German or Japanese cars is easy, finding French or Italian high mileage cars is much more rare.
And then goes on to say this is mostly limited to rust, which French cars used to do pretty badly but using better quality steel, paints and in some cases galvanization cured that problem.
French cars haven't rusted in decades. But that doesn't mean their assembly quality is better than the Japanese.
And I'm not convinced that Japanese cars are so bad in the rust department either.
The last batch of really badly rusting cars - ironically - were Mercedeses from the early 00's. Mercedes totally missed the boat on the water based paint front and got it dramatically wrong leading to a ton of re-work and expensive warranty issues.
I have to disagree, even though my knowledge is anecdotal.
All our Citroen cars NEVER showed any sign of rust. Our BX was 15 years old, when the hydro-pneumatic system fell apart. Citroen are known for excellent attention to corrosion protection on essential parts. I know a BX nearby from that era (must now be ~30 years old) that seems to be flawless.
Our VW Golf IV we currently own has had almost no exposure to the winter in his 17 years, apart from the last 2-3 years. He began rusting badly last winter, this will unfortunately end very soon.
High mileage German cars are available (I can only speak for middle Europe), because they have extraordinary value degradation (in terms of slow degradation), i.e. people still want them, because they are supposedly longer lasting, and supposedly better quality.
Maintenance statistics speaks otherwise. And god repairs on VWs are expensive. Just a new key fob is easily 5x as expensive as on a Citroen!
Edit: This blog-post [1] would indicate that my information is no longer valid. But then there is this post as well [2], which could be due to individual maintenance costs being higher for "luxury brands". Needs more research.
BX was one of the first cars to have a lot of plastic in the body, you still see them occasionally.
Citroen CX and DS as well as 2CV were notorious for being rust buckets, the ones that are left have had tons of money poured into them. CX and injected DS were notorious for catching fire. Another major issue with the CX was euphemistically labeled 'gearbox separation' (I've actually had that happen to me on one of the two CX's that I owned, a 2400, super nice car but with the gearbox landing on the street it didn't get very far). The second one suffered a collapsed piston. All in all not the best score :), and that's before we get to rust issues. They were beautiful cars though, and super comfortable.
The more modern ones did not rust so much because Citroen got their rust problem under control somewhere in the mid 80's early 90's, hydraulics were a lot better too. The C5/C6 were probably the best cars Citroen ever made before they really became boring, and the DS is still a head turner after 60 years since it was first introduced, and it will always be my favorite car, even if I no longer drive them. On the plus side, my current car has the same suspension.
Parts for German cars are indeed ridiculously expensive but then again, they fail less frequently.
High mileage vehicles are the best way to check how reliable a car is, if it works out well the drivetrain and engine will outlast the chassis. I've had VW Golfs (older diesels) with 250K plus on them and a whole slew of Mercedeses, never a problem that caused the car to be stranded. I've never owned a BMW so I can't say anything about those but my French cars have been a long list of all kinds of interesting problems. I didn't mind, it taught me a lot about working on cars (and doing an engine rebuild on a DS is something special), but they never were very reliable. Oh, and I forgot to include one Citroen in my list, Xantia diesel which was fairly low mileage (180K) when it spectacularly blew up the head somewhere on the way back from Switzerland. That wasn't a fun trip at all.
There were older Citroen cars with a lot of plastic/composite parts.
For example, the Mehari used a lot of plastic parts (ABS) and is from the late 60ies.
It didn't prevent rust completely however. For example, the Mehari was as prone as the 2CV to have a chassis breakup.
My father actually got one with a broken chassis (in fairness, more due to the fact it has been driven in very rough roads around South Europe and Asia Minor in the 70ies) and spent a summer disassembling it completly to replace the chassis (he still has a beautiful photo with all the parts laying around).
One thing to keep in mind is that the Mehari, as the 2CV, was designed to be a very simple and cheap car from the 60ies (the 2CV design even traces back to the 30ies). This actually somewhat wonderful as it's possible for a single person to service these cars alone with a few basic tools if he knows a thing or two.
Mehari and 2CV share a very large chunk of their design. And that was a very special car, I'd love to have one but they are hard to find in good condition.
Oh, you were talking about pre-80ies french cars...
Yeah, I remember my dad telling me those were known to rust almost immediately, and they apparently (to his perception, based on the cars we owned) not only got their act together, but excelled at it, somewhere end of the 80ies/beginning of the 90ies.
And that is true, the BX has considerable plastic parts (although only the front hood and the front mudguards, which is awesome if you ever bump something, nothing happens!), the non-visible chassis is still metal and very rust-safe.
On a side note: Our Renault 21 Nevada from the early 90ies was a different beast... I think almost everything on it had to be replaced randomly, and although it made it to 270k or more (I think), my dad was happy to leave it behind and he only kept it because it was a company car.
Renault never really got their quality control in order, they are still hit-and-miss today. If you're lucky you will have a fantastic car if you don't it will nickle-and-dime you to death. I've had a couple of Espaces, I absolutely love the form factor but the reliability and general quality are horrible.
German cars are substantially better in quality, and finding high mileage German or Japanese cars is easy, finding French or Italian high mileage cars is much more rare.