Quote: Where the diameter of the fuel line comes into play is the velocity of the fluid within the line. Head losses or pressure losses are related to velocity squared divided by 2 x force of gravity times the head loss coefficient of the tubing. So essentially a larger diameter tubing reduces the fuel velocity and the pressure losses.
The mass/inertia of the fluid does come into play, that's why the density is in the the equation. Area doesn't factor in at all.
