10 Best Fuel Injection Oil Supply Lines

Review Analysis Conclusion

Based on analysis of 18,073 reviews across the ten ranked fuel injection oil supply lines, a few clear patterns emerge. Push-lock NBR hoses in 5/16-inch and 3/8-inch inner diameters dominate the volume of feedback, with consistently high marks for flexibility, ease of cutting to length, and resistance to standard gasoline. PTFE-lined 6AN kits, while backed by smaller review pools, earn strong sentiment from E85 and forced-induction users who specifically call out permeation resistance and clean AN fitting assembly. Application-specific direct-fit kits (such as the Harley-Davidson Touring line) attract the fewest reviews but show concentrated positive feedback from owners of the exact years and models they target.

Across the entire field, negative feedback clusters around three recurring themes: stiff braided hose that is hard to route in tight engine bays, push-lock fittings that weep when clamps are omitted or under-torqued, and direct-fit lines advertised for broader model ranges than they actually cover. Hoses that bundle the right adapters, fittings, and clear instructions tend to score higher regardless of price tier.

If you are choosing between two close-ranked options, compare the included hardware and the typical installation described in reviews rather than the headline working pressure. A 300 PSI hose without the correct fittings will underperform a slightly lower-rated hose that ships ready to install.

Buying Guide

Picking the right fuel injection oil supply line is less about brand prestige and more about matching the hose to your fluid, pressure, and routing environment. The sections below walk through the practical decisions that separate a dependable installation from a chronic leak.

Quick Comparison

Sizing and AN Equivalents

Two sizing conventions show up in this category: fractional inch inner diameter (ID) and AN dash numbers. Stock EFI lines on many cars and trucks sit at 5/16" or 3/8" ID, which is why push-lock hoses in those sizes are the most heavily reviewed. Performance and forced-induction builds often move to 6AN or 8AN because AN fittings seal more positively at higher pressures and the braided jacket resists abrasion and chafing.

A handy rule of thumb:

• 4AN ≈ 1/4" ID
• 6AN ≈ 3/8" ID
• 8AN ≈ 1/2" ID
• 10AN ≈ 5/8" ID
• 12AN ≈ 3/4" ID
• 16AN ≈ 1" ID

Before ordering, measure the port threads on both ends of the planned run. Thread pitch and seat angle (AN-37° flare, inverted flare, NPT) are not standardized across the industry, and an AN fitting that looks right can leak if the seat geometry does not match. Buy slightly more hose than your measured path needs—tight bends, engine rock on its mounts, and service loops all consume extra length.

Material Tradeoffs

• NBR (nitrile butadiene rubber): Affordable, flexible, and widely rated for gasoline and diesel. Standard NBR can swell after long exposure to high-ethanol fuels and some synthetic oils.
• CPE (chlorinated polyethylene): Better heat and ozone resistance than basic NBR, often paired with stainless or nylon braid. Stiffer than push-lock rubber.
• PTFE (Teflon): Chemically inert, handles E85 and methanol without swelling, and tolerates higher temperatures. Typically the most expensive option and the stiffest without heat-assist tools.
• Stainless or nylon braid: Adds abrasion resistance and burst strength but adds bend-radius limitations; a 90° or 45° fitting is usually required to clear valve covers, frame rails, or suspension components.

Best For / Avoid If

Best for these scenarios:

• Daily-driver EFI repair or restoration where stock routing must be preserved.
• E85, ethanol-rich, or methanol-fueled builds needing low-permeation hose.
• Turbocharger oil feed and return lines operating at elevated pressure.
• Remote-mounted oil coolers and large-bore fuel systems where flow volume matters.
• Direct replacement of a known OEM fuel injection line on a specific year/model.

Avoid or reconsider if:

• You plan to run a fuel the hose is not rated for (some stock rubber hoses are not approved for E85 or methanol—verify the spec sheet).
• The routing requires very tight bends in a stiff PTFE or braided hose—plan for angled fittings.
• The kit ships without fittings and your existing adapters do not match the new hose’s dash size.
• The working temperature of your engine bay routinely exceeds the hose’s published rating.

Pressure, Temperature, and Safety Margins

Most push-lock fuel and oil hoses in this category are rated for at least 300 PSI working pressure. That comfortably exceeds port-fuel injection (typically 40–60 PSI) and even most direct-injection systems. Turbo oil feed lines see pressure spikes from the engine’s oiling circuit, so a 300 PSI rated hose is often acceptable for mild setups; high-output turbos or restricted-drain setups warrant PTFE or stainless-braided hose with a higher margin.

Remember that temperature lowers the effective pressure rating of any hose. A line rated at 300 PSI at 70°F may derate significantly at sustained under-hood temperatures of 250°F or more. Verify the printed rating on the actual product you are buying and confirm that fittings, hose ends, and any adapters are rated for the peak pressures your system will reach.

Installation Notes

Push-lock hose is the fastest installation: push the hose onto a barbed fitting and secure it with a quality hose clamp. Push-lock is forgiving and ideal for repairs, but a loose clamp is the most common cause of slow weeps. AN hose demands clean square cuts, proper socket-and-nipple assembly, and torque to spec; once built, AN lines are reusable and more secure under high pressure.

When evaluating a kit, look for what is included in the box: bulk hose only, hose plus ends, or a full kit with straight, 45°, and 90° fittings plus adapters. Converting from stock hard lines to braided hose almost always benefits from a complete kit so you are not making extra trips for fittings or adapters.

Common Mistakes

• Skipping the clamp on push-lock hose. Without a clamp (or with the wrong clamp style), push-lock hose can weep under sustained pressure.
• Routing braided hose against exhaust manifolds or sharp brackets. Even stainless braid can wear through over time—use Adel clamps or padded separators.
• Underestimating required length. Engine rock, service loops, and bend add-up often require 12–18 inches more than the measured straight-line distance.
• Mismatched fittings. Mixing AN dash sizes or seat angles (for example, an AN-37° fitting on a NPT port) is a frequent source of slow leaks.
• Buying a direct-fit kit without confirming the exact sub-model. “Fits Touring” can mean very different things across model years.

Maintenance and Inspection

Inspect fuel injection oil supply lines at every oil change or seasonal service. Look for surface cracking, hardening, swelling, or bulging near fittings. Ethanol fuels shorten rubber hose life, so PTFE-lined options generally last longer in modern pump-gas environments. A faint fuel smell in the garage almost always points to a fitting—trace every connection methodically before assuming the hose itself has failed.

Keep hose away from exhaust components and sharp edges. Use padded separators where the line passes through the firewall or alongside suspension components. Leave a small service loop at each end so engine movement does not load the fittings.

FAQ

Can I use push-lock hose for a turbo oil feed? For mild setups and low-pressure feeds, yes—many builders do. For higher-output or restricted-drain turbos, a PTFE or stainless-braided line is the safer long-term choice.

Is PTFE hose compatible with E85 and methanol? Yes. PTFE is chemically inert and is the go-to liner for ethanol-rich and methanol fuels where standard rubber would swell or permeate.

Do I need new fittings when switching from rubber to braided hose? Almost always. Braided hose uses AN-style hose ends that are not interchangeable with barbed push-lock fittings.

How often should fuel injection oil supply lines be replaced? There is no fixed interval. Inspect them at oil changes and replace at the first sign of cracking, hardening, swelling, or fitting weep.

What is the difference between 6AN and 3/8" hose? A 6AN line has approximately a 3/8" inner diameter, but the fittings and end geometry are different. 6AN uses an AN-37° flare seal, while 3/8" push-lock hose uses a barbed stem and clamp.

Final Recommendation

For daily-driver EFI work and OEM-style replacements, the 5/16" and 3/8" NBR push-lock hoses at the top of our list offer the strongest combination of verified durability, easy installation, and broad fitting compatibility. They are SAE-rated and simple to cut to length.

For E85, methanol, forced induction, or race-only setups, step up to a PTFE-lined braided kit. The 6AN PTFE options in our rankings ship with the fittings and adapters needed for modern fuel injection systems and resist the permeation that degrades standard rubber over time.

Builders plumbing large oil coolers or high-volume fuel systems should look at the 16AN braided kit, while those restoring a specific-year Harley-Davidson Touring model or another OEM application should match the direct-fit kits to their exact vehicle. Confirm your fitting sizes and fuel chemistry before ordering, and always buy a little extra length to absorb the realities of under-hood routing.