Installing Fumoto oil drain valve, question on gasket and crush washer
 

I'm about to install the drain valve and it comes with a rubber gasket. I got a new crush washer in anticipation for this install, but I am now questioning the order these 2 would be installed. Is it even advisable to use both,. If so, what is the install order (pan>crush washer>rubber gasket>drain valve)?
Thanks.

IIRC, I just used the OEM crush washer.

I'm no expert but using 2 washers doesn't seem like a good idea engineering wise.

A "crush washer" does just that.
It would "crush" a secondary rubber washer to useless bits before it did it's primary job.

My FuMoto came with a fiber washer a few years ago.
I used that along with clean surfaces and a slight film of RTV sealant.
I don't anticipate needing to remove it again for the life of the oil pan.

I don't recall exactly how wide the sealing surface is on the valve itself,
but I don't think that it is wide as the original pan bolt.

If the valve was supplied with a washer, use that instead.
Don't torque it to metal bolt / metal washer specs. That would split the rubber.

I used the included rubber washer.

Do not install both. Crush washer will not "crush" properly with a rubber washer next to it.

When you tighten down the valve, make sure you tighten it with a crescent wrench on the body of the valve and not a socket on the hex end of the valve or you will damage it:http://www.fumotousa.com/installation.php

Enjoy your easy oil changes!

I just used the fiber washer that came with it, going on 3 years soon with no leaks.

This.