I got myself a used Flashforge Dreamer dual-print head 3D printer and I've been doing a LOT of experimentation with it, printing replacements for broken parts around the home, a copy of the first ratchet wrench uploaded to the International Space Station for printing and use, and other cool things. One thing I came up with is this:

https://www.thingiverse.com/thing:4459377

It's a ring that is inserted over the thread of the fuel cap. Take the existing soft seal out first, insert this ring and then slip the soft seal on top of the ring. I did it because I was getting P0455 errors all the time about an evaporative fuel system leak (the famous $100 fuel cap scam). The idea here is to make sure the soft seal seats properly and tightly on the fuel tank filler neck. The error is now gone, haven't seen it again in a while, cost me maybe 25 cents and saved me the cost of a new cap (just replacing the soft seal didn't fix it). I printed this with PLA filament. Don't use ABS as it is likely reactive to gasoline fumes (acetone melts it). Don't use TPU or other soft filaments either, this is supposed to be hard so as to press the factory soft seal firmly against the lip of the filler neck.

 

Cool, same annoying problem, but don't have a 3D printer yet. A new capped helped, but the code still pops up occasionally, so I greased the seal. That helped a little more.