Unheated fuel-line assembly and method of detecting leakage at and/or in a fuel line

The invention relates to an unheated fuel-line assembly, in particular for use in a motor vehicle, where an inner tube is provided as a fuel line and an outer tube is provided that surrounds the inner tube with a spacing a. The inner surface of the outer tube that faces toward the inner tube is formed with a plurality of grooves that extend at least over a portion of the length of the outer tube longitudinally of the outer tube.