Crush washers are made from ...
 

Crush washers are an essential part of working on a Pickup or 4Runner. They are one-time-use and must be replaced whenever a pressurized fuel line is opened. They cost only a little more than a dollar each https://parts.lakelandtoyota.com/sho...rimLevel=18380, but it costs about $10 to have them shipped to you (OR, a brick and mortar dealer knows the cost of shipping, and charges accordingly).

On this forum, I've said that they are only available from the dealer. I've said I thought they were made from aluminum, but others have suggested copper. Could they be tinned copper?

I took a removed crush washer and sanded it enough to remove any possible tinning. Nope, "silvery" all the way through. I'm calling them aluminum. Copper washers seem to be used more in brake line applications, SFAIK.

It turns out that both copper https://www.aliexpress.com/item/100p...891162514.html and aluminum https://www.aliexpress.com/item/Hot-...964058902.html washers are available in assortments.

What do you think they are made of? Do you have a better source for them?

Just so you know, I measure them at 10x14x1 (CSI), 18x23x1 (Fuel Pressure Damper), and 12x16x1 elsewhere.

This kit worked perfect for my 92 22RE. The 3 or 4 sizes I needed were an exact for every crush washer under the hood.

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

I think I remember reading something about different crush washers for drain and fill plugs underneath the truck depending on what the housing was made of (transmission vs diff) maybe someone can verify this

Yes, there is a note on the Marlin crawler website about that, for the axle housings or any iron-based housings they give you a steel "gasket" and an aluminum "gasket" for the tcase & transmission.

I don't have a single crush washer, they are all just flat, soft material. No leaks yet!

But then, I drive the thing home once with leaky injector rubber bushing. Din't catch fire either. :p (DO NOT TRY THIS AT HOME) :)

The washers can be made from both, Their application can justify the material. Things with less clamping force, like a drain plug, usually will use aluminum. Aluminum is softer and will deform enough to seal before stripping an oil pan. A copper one might strip. Things like brakes though, which might see 1000psi, a copper washer will be used due to the extra clamping force on the banjo bolt. If an aluminum one were used it would deform too much and cause a leak.

In a pinch I have reused the copper crush washers. I make sure to mark them and when reusing, flip it over so it deforms again when crushed.

I'd shy away from reusing the aluminum ones though.