If you’re looking for 5/16″ fuel line, there’s a good chance your machine is EFI — electronically fuel injected rather than carbureted.
That distinction matters more than the number does. 5/16″ isn’t a bigger version of 1/4″ that you upgrade to. It’s a different fitment for a different fuel system, and putting it on the wrong machine causes the exact problem you were trying to avoid.
This page is about that boundary. Starting with the full picture? full size chart.
Why 5/16″ Is Not “Just a Bigger 1/4”
A carbureted small engine pulls fuel through the line under slight vacuum. An EFI system pushes it under pressure through a different plumbing arrangement. The hose has to match the fitting on that system — not the one you wish it were.
Kohler’s 25 111 37-S fuel line is marked EFI Only. That marking isn’t marketing; it’s the manufacturer telling you where the part belongs.
Here’s how the mismatch plays out:
5/16″ ID on a 1/4″ fitting — the hose is too loose. It slides on with no resistance, the clamp can’t close the gap, and it either seeps or pulls air into the carburetor. Air in a carbureted fuel system shows up as a lean condition, rough idle, or a machine that won’t stay running.
1/4″ ID forced onto a larger fitting — the opposite problem. The hose stretches to get on, the liner thins at the barb, and it splits or leaks at the connection.
Either direction, you end up chasing a fuel problem that is really a size problem.
If your machine is carbureted and takes 1/4″, the 1/4″ fuel line page is the one you want.
Machines That Take 5/16″
The honest answer: newer EFI-equipped equipment. That’s the category, and it’s a narrower one than 1/4″.
When we say EFI, we mean small engines with an electronic fuel injection system — typically newer riders and equipment built in the last several years. The factory plumbing on those machines often runs rigid fuel line with quick-connect fittings rather than a length of rubber hose.
That last point is worth pausing on: if your EFI machine uses hard line and quick-connects, a length of 5/16″ rubber hose may not be the right replacement part at all. Check what your machine actually has before ordering.
The Spec Sheet for 5/16″ Fuel Line
| Spec | Value |
|---|---|
| Inside diameter (ID) | 5/16″ |
| Outside diameter (OD) | — (measure yours; see below) |
| OEM part number reference | Kohler 25 111 37-S — marked EFI Only |
| Working pressure | 50 psi max where the line falls in the SAE J30 R6/R7 ≤3/8″ band |
| Burst pressure | 250 psi min (SAE J30 DEC2008) |
| Common applications | EFI-equipped small engines (newer riders, injection systems) |
Three things to take from that table:
5/16″ appears on EFI machines. That’s the whole story behind the size.
We’re not publishing an OD number. Outside diameter varies by maker and wall construction, and we’d rather leave the cell empty than print a figure we can’t back up. Measure yours.
When in doubt, measure the fitting — not the old hose. The old one has stretched. how to measure your fuel line shows the two-minute version with a caliper.
Clamp and Routing Notes
Because OD varies, you can’t buy a clamp by size alone on this hose — you have to measure the hose you’re holding.
Once you have the OD:
- Match the clamp to that number, not to the “5/16” on the package.
- Prefer smooth-band clamps around fuel line. Worm-gear clamps with a cut slot can chew into the liner as they tighten.
- Replace the clamps with the hose. A fatigued clamp on a new hose is a leak waiting to happen.
On routing: EFI systems often run lines closer to heat sources and tighter than carbureted setups. If you’re replacing a section, follow the original path where you can, and keep bends gradual — a kink starves the system just as badly as a loose connection.
Three 5/16″ Mistakes
1. Putting 5/16″ on a carbureted mower. This is the big one. It’ll slide on, feel “close enough,” and then leak or draw air. If your machine is carbureted, it almost certainly takes 1/4″ or 3/16″.
2. Assuming bigger is safer. A larger ID doesn’t give you margin — it gives you a loose fit. Fuel systems don’t benefit from extra clearance the way a coolant hose might.
3. Trusting the printed ID alone. The number on the jacket tells you the size, not whether the hose is rated for your system. Cross-check the machine’s parts list before you commit.
FAQ
Is 5/16 fuel line the same as 1/4?
No. 5/16″ is a larger inside diameter used on EFI-equipped engines. 1/4″ is the standard carbureted small-engine size. They’re not interchangeable.
What does “EFI Only” mean on a fuel line?
It means the manufacturer specifies that part for electronically fuel-injected engines — Kohler’s 25 111 37-S carries this marking. It’s a fitment designation, not a quality grade.
What OD is a 5/16 fuel line?
It varies by manufacturer, and we won’t print a number we can’t verify. Measure the hose or the fitting with a caliper — that’s the only answer that’s correct for your machine.
Can my carbureted mower use 5/16 fuel line?
Don’t. A carbureted engine takes a smaller line (typically 1/4″, sometimes 3/16″). 5/16″ will fit loosely and cause leaks or air ingestion.
How do I know if my machine is EFI?
Check the engine model number against the parts list, or look for fuel injection hardware — an injector, a fuel rail, or a high-pressure pump. If it has a carburetor, it’s not EFI.
Need 5/16″ fuel line for an EFI machine? fuel line kits cover the common small-engine sizes with clamps included.
*Ready to buy? Get the fuel line kit →*