Same protection as uk cars and German cars are built the same as they’re here in uk the only difference is that Japan often had options we didn’t or engines we didn’t get. I looked at a cls350 from Japan as it had the petrol v6 whereas in uk we never got that. I think Japanese also like their colour a bit more so you get some interesting combos.
Rust wise it’s simply the fact that many parts of japan don’t use salt on the roads so the cars never rust as much. My 20 year old Toyota crown for example was rust free to a point that bolt threads were as new on the side and had the factory “paint” marker marks everywhere. At 140k km that is.
But parts of Japan that get a lot of snow etc can also have rusty cars.. I’ve seen some proper rusty ones.
Cheers, I knew you'd be the man with the answers
