Is this where I get to put in my preference for using analytical data from your specific bike and oil?
Just speculating here because I haven't changed the oil yet with only 70 miles on the bike, but is it an actual crush washer or the solid copper type?
My Yamaha had the actual crush washer style from the factory which I promptly replaced with the correct size solid copper washer at the first oil change. That replacement washer is still on there at 75,000 miles after a bunch of 5000 mile oil change intervals. I plan on using the 5000 mile oil change interval on the NC700 also because it is so much easier to remember changes at that interval.
Like others have mentioned, I also order a bunch of parts at the same time so that shipping on the $0.50 crush washers would be negligible. But I'll probably still use a solid copper sealing washer just to avoid having to pry off a crush washer everytime.
I doubt that any manufacturer uses solid copper on an aluminum engine block. copper on aluminum creates a galvanic corrosion. If Yamaha uses them against aluminum they probably have a zinc coating to prevent that.
My understanding of the oil drain plug is that its primary purpose is to seal and keep oil from leaking out. This is very easily done with a hardened steel plug and an aluminum contact surface that are machined flat and smooth.
The problem is that these are frequently loosened and tightened by non-mechanical type people, and they are often over-tightened. The washer is not necessary to seal the oil in. It is there to protect the aluminum engine block and the aluminum threads that the drain plug screws into. Its purpose is to "give" when someone over tightens, rather than damaging the threads.
Someone like myself, who always changes his own oil and never over tightens will never "crush" the washer, and thus it will never need replacing. I don't need a torque wrench, I just know how much to tighten. Tight enough to seal and not come loose, and no tighter. I don't know what Hondas torque specs are, but if they are anything like how tight they had the oil filter on my NC, they are either way too tight or they are not followed by the assembly people
Once the washer has been crushed, it must be replaced. Aluminum is soft and malleable (which is why it is used here), but pushed too far will crack and tear. Once it cracks, your seal is gone. You might just have a slow drip. Or it could leak out the entire pan.
As far as annealing, I do not see the point in trying to salvage a .60 cent item. Spend the .60 cents and get a new one.
If you are a person who likes to over tighten things, and / or if the Honda specs tell you to over tighten the drain plug (to be really really safe maybe?), then yes you might want to keep extra washers on hand.
I don't plan on replacing mine unless it really needs it, which it never will, because I will be the only person changing the oil on this bike
