[myself248]

Aluminum is hell to terminate. It basically requires ultrasonic welding; every trade-show has folks hawking various crimp terminals that're meant to break through the surface oxides during the crimp cycle, but not a single automaker has been swayed enough to use it on normal wiring.

The reliability concerns really add up with flexing fatigue, too. It's one thing to put aluminum wiring in a house where its only flex is due to thermal expansion, and it has a hard enough time coping with that it's still a special category in home insurance, to say nothing of a vehicle that's going to spend the next ten-plus years bouncing over the road.

Furthermore, you basically can't modify aluminum wiring. In-line splices and solders are virtually impossible. While that's irrelevant for manufacturing, it hits the aftermarket pretty hard, including dealer mods, and of course, dealer repairs. That can be worked around but it would require communication between branches who don't normally talk, and it just adds friction to any possible aluminum migration.

I've seen aluminum in a single very-heavy-gauge battery cable for a car that put the battery in the back, with ultrasonic-welded terminals on both ends, and that's it. Everything else in that car was copper.