There seems to be some confusion here between flare fittings and compression fittings.
Brake lines use flare fittings. The end of the line is actually flared out to match the cone on a flare fitting. It'* a nice positive-retention method of attaching high pressure lines. Flare fittings are also used in household natural gas lines for the reason that they are very reliable.
Compression fittings are different. In a compression fitting, the line is retained and sealed (hopefully) by a brass ring, which is "compressed" or crushed onto the line when the fitting is tightened. These are not as reliable, and are usually only used on water or air lines, non-critical things like that. They are never, ever, to be used on brake lines.
Either might work on a fuel line, but I'd be more comfortable using a flare fitting for the above reasons.
Hope that clears things up.
I'm Jon. I'm completely stock, no mods.
1993 Bonneville SSE 191,000 miles "The Work Beater" Imperfect but quite tolerable. Stock.
1996 Buick LeSabre Limited, 181,000 miles "The family car" Custom CAI, F41 Sways.
Sold/dead, but not forgotten: 1989 Bonneville LE "Bonnie, the Sport Utility Car" STB from '92-'99 Bonnie, Delco (Type II) Ignition system
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