Efi fuel return line size?

[Jr]

Good day,

What's the point of running a return fuel line smaller than the feed line? I was just wondering...

[Rhino]

Some fuel is burned, as such the requirements for the return line are less than the feed.

In the case of an engine driven, mechanical pump there is also a secondary reason. The supply side is under vacuum, the return under pressure. It's much easier to push fluid through a line than it is to pull it.