I need to replace some rotted under-body lines. I'd like to use something easier to bend than old-school steel tubing - in particular, AGS' Nicopp. At that link, the blurb for Nicopp line doesn't mention fuel, while the Poly Armour one does. OTOH, this Nicopp page does include fuel.

What makes me wonder is, (a) all 'headline' references to Nicopp (and Poly Armour, for that matter) call it brake line; (b) for something that seems ideal for the application, I'm not finding references to its use it for fuel line. It just feels strange to me.

... And, if it can be used for fuel, can it be used with a compression fitting?

EDIT: re compression fittings, I was wondering if the softer tubing might somehow not properly support the compression ring; and, also, if the O.D. of the Nicopp might be different than that of steel, such that it could still work in a flared fitting, but again not support the compression.

4 Answers 4


The second page you provided says:

NiCopp® has been used on hydraulic/fluid transfer systems on vehicles where steel lines and tubing are commonly used. This includes brake, fuel and transmission systems.

There should be absolutely no issue using the NiCopp lines for fuel.

As for compression fittings, remember that the flared fittings shown on the page are for high pressure like you'd need for brake lines. As long as you get the correct size compression fittings it should work just fine for fuel, as long as you aren't using it for direct injection lines. Normal fuel pressure levels should be well under 100 psi. A compression fitting is going to work peachie.

  • They mean cupronickel but made a new name. Cupronickel is copper plus 10 to 30 percent nickel . US coinage is mostly cupronickel . Strength depends on cold work , generally stronger than any brass. Very corrosion resistant. Jun 11, 2020 at 22:46

I used Ni-Copp lines to replace the transmission cooling lines on my truck. I double flared the ends that went to the cooler, but used compression unions to tie them to the remaining 4" of steel lines at the transmission. The compression unions leaked like a sieve, no matter what I did with them. The problem is, that the Ni-copp material is so soft, that the ferrules in the unions can't "Bite" on the line. They just compress the line as you tighten down the compression nuts. When I dismantled the assembly, the ferrules just slid off, as if no tightening at all, had occurred. Finished the job with high pressure hose & double fuel injection clamps. It's been fine now, for about two years.


If you want to use compression fittings on the nicopp use the inserts you would typically use with hose to help keep the softer line from collapsing under the ferrel... or just flare it like your supposed to


Ni-copp is very likely actually cupronickel; 70 % Cu , 30 % Ni. Think of it as extra strong, extra corrosion resistant copper.

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