AN-6 Hose and Fittings: A Complete Guide

AN-6, also written -6AN or dash 6, is one of the most widely used sizes in motorsport plumbing. It is the default choice for fuel lines, power steering and lighter oil circuits. This guide explains what the number means, what thread AN-6 uses, and how to specify a line.

What the AN number means

The AN number refers to the outside diameter of the equivalent rigid tube, measured in sixteenths of an inch. AN-6 corresponds to 6/16", which is 3/8" tube outside diameter.

This is the part that confuses people: the AN number is not the hose bore. It is a size designation carried over from the original military tubing standard. AN-6 hose has an internal diameter of roughly 8mm, not 3/8".

AN sizes at a glance

The 37 degree flare

AN fittings seal on a 37 degree flare, also called JIC. The male fitting has a 37 degree cone and the female has a matching seat, and the two clamp together metal to metal. No sealant, no O-ring, no tape on the flare.

This matters because 45 degree SAE fittings can share the same thread. A 45 degree cone in a 37 degree seat contacts on a narrow line rather than across the full face. It will often hold when static and weep under pressure or vibration. If a joint will not seal despite correct torque, mismatched flare angles are the first thing to check.

AN fittings also do not need PTFE tape on the flare. Tape belongs on tapered pipe threads such as NPT or BSPT, never on a flare face.

What AN-6 is used for

• Fuel lines — AN-6 flows enough for most naturally aspirated and moderately boosted engines. Feed and return on a typical fast road or club race build
• Power steering — both pressure and return, commonly with adaptors to metric O-ring ports
• Oil return and breathers — low pressure, moderate flow
• Turbo oil drain on smaller units — though AN-10 is more usual

Choosing hose: PTFE or rubber

PTFE lined hose has a solid PTFE inner with a stainless braid over it. PTFE is chemically inert, so it handles ethanol blends, methanol and modern fuels without degrading, and it does not permeate — no fuel smell. It is stiffer and needs a larger bend radius.

Rubber lined hose is more flexible and easier to route in tight spaces, and cheaper. It is fine for oil, water and pump fuel, but standard nitrile permeates over time and is not suited to high ethanol content.

For anything inside the cabin, use PTFE. Permeated fuel vapour in an enclosed space is a genuine hazard, not a comfort issue.

Note that PTFE and rubber hose take different fitting types. PTFE hose ends use an olive or ferrule that bites into the PTFE liner. Rubber hose ends use a cutter style that grips the braid. They are not interchangeable, so specify hose and fittings together.

Fitting angles

AN-6 hose ends are available straight and in 45 and 90 degree bends, with 30, 60 and 120 degree options in some ranges. Using the correct angle at the fitting rather than bending the hose keeps the run shorter, avoids kinking, and reduces stress at the joint.

PTFE in particular does not like tight bends. If a run needs to turn sharply near a fitting, use an angled end rather than forcing the hose round.

Adaptors to metric ports

Most vehicles do not have AN ports from the factory, so adaptors bridge the gap. The common ones for AN-6:

• M14 x 1.5, M16 x 1.5 and M18 x 1.5 O-ring tip — standard on power steering racks and pumps. The O-ring does the sealing, so these are torqued to seat the O-ring, not crushed tight
• M12 and M14 banjo adaptors — where the original connection is a banjo
• NPT adaptors — for fuel pumps, filters and regulators. NPT is a tapered thread and does need sealant on the threads
• Bulkhead fittings — for passing a line through a panel with a solid anchor

Assembly notes

• Use aluminium AN spanners. Steel spanners mark anodised fittings, and a rounded fitting is difficult to remove later
• Cut braided hose with a proper cutter or a cut-off wheel with the hose taped either side of the cut. A hacksaw frays the braid
• Assemble dry on the flare. A little oil on the threads makes tightening smoother without contaminating the sealing face
• Do not overtighten. AN flares seal on contact, and excessive torque distorts the cone
• Support long runs with P-clips every 300 to 400mm to prevent chafing and fatigue

Specifying a line

To order or build an AN-6 line you need: hose type (PTFE), length, fitting at each end, angle at each end, and any adaptors required at the vehicle side.

Measure the route the hose will actually take rather than the straight line distance, and allow for the fitting length at each end.

Need help specifying?

Send us the details of your application, or a photo of the ports you are connecting to, and we will confirm the fittings and adaptors before you order.

Browse AN-6 hose and fittings, power steering hose and fittings, AN-4, AN-8, AN-10 and AN-12.