Actually the opposite, annealing softens the aluminum, increase its ductility:I’m not a metallurgist but how would annealing aluminium improve the seal? I was under the impression that softer metals are better for this purpose and wouldn’t annealing harden the metal?
https://en.wikipedia.org/wiki/Annealing_(materials_science)
I'm not a metallurgist either, but several years ago I was struggling to seal up brake calipers and a local friend who is a metallurgist suggested I anneal the washers I had. Worked like a charm and I learned a lesson about generic copper washers that may or may not be properly annealed for sealing.
Never used one.How do you feel about plastic drain bolt washers?
Lack of stats isn't how evidence works.There is no reason you cannot reuse a drain plug gasket that is in good shape. Again, this has been done hundreds of millions of times without issue. That's a lotta evidence. I have no stats, but my guess is more have been reused at least once than not.
It's best practice for any mechanic who's worth a **** to replace copper / aluminum crush washers. These mechanics love lub-jockies that re-use these gaskets since it generates more work for them.
Aluminum / copper form a seal by being crushed. Sure when properly torqued there should be enough crush left for a second use, maybe.... maybe not. For less than $1 a year why is this even a debate?
What's next, reusing condoms?