What is the correct sealant to use on diesel fuel line threads?
 

I'm installing an aux fuel tank plumbed to my fuel filler neck. The kit from RDS doesn't tell me what, if any thread sealer I should use on the threads for the shutoff fitting at the tank, or the check valve at the filler neck?

I'm not sure if teflon tape is ok? Does anyone know what I should use on these threads. Everything is aluminum.

I searched for this, but couldn't find anything.

Permatex Teflon sealant would do the job, if you feel you need one at all.

Permatex makes a few thread sealant compounds that work well around diesel and gas. Also high temp thread sealants for engine sensors like temp, 02 exc.

Make sure you don't use a thread locker where you want a sealant!

First thing to think about is the type of fittings you have. No sealant is used on flare fittings, compression fittings, and several other types, but a npt fitting requires it. Assuming you do need sealant,i believe teflon tape would hold up BUT its likely to have some loose pieces of tape inside that may clog up the strainer, so I would use a sealant that you apply as a liquid such as the permatex. The package should specify what it is and is not suitable for