What type of hose is used for turbocharger oil feed lines?

Turbo oil feed lines carry pressurized engine oil into the turbo's center housing, where the shaft bearings live. That oil lubricates the bearings and pulls heat out of the turbo. The line sits near the exhaust manifold and turbine housing, so surface temperatures can exceed 300°F. Engine oil pressure at the feed inlet usually runs between 30 and 80 psi depending on engine speed and oil temperature. Any hose used here has to survive heat, pressure, and hot oil without swelling, softening, or shedding material into the bearing.

The standard choice: PTFE-lined stainless braided hose

For most aftermarket turbo oil feed lines, the right hose is a PTFE-lined stainless steel braided hose. The PTFE inner liner is a fluoropolymer that handles both conventional and synthetic engine oil at continuous temperatures above 450°F. The stainless steel wire braid around it stops the hose from expanding under pressure and protects the liner from cuts and abrasion. Many OEM turbo engines use a formed steel hard line instead, which works well but offers less flexibility for routing and service than braided PTFE hose.

What not to use

Standard silicone hose is not an oil hose. Engine oil makes silicone swell and lose strength. The same rule applies to unrated rubber fuel hose, heater hose, and clear PVC or polyurethane line. Use an oil-rated hose for the feed. If the hose is not specifically rated for hot oil under pressure, it does not belong on a turbo oil feed.

Rubber-lined braided hose: the budget trap

Rubber-lined stainless braided hose looks similar to PTFE braided hose, but the inner liner is a different material. Heat from the turbo bakes the rubber, hardens it, and cracks it. Those cracks shed small rubber particles that can clog the turbo's oil restrictor or score the bearing journals. Ball bearing turbochargers, which use a small restrictor to limit oil volume and pressure at the center housing, are especially sensitive to debris, so any rubber particles from a degrading hose liner can block that restrictor and starve the bearing. The PTFE liner does not degrade in hot oil the way rubber does. It also has a smoother inner surface, so less flow restriction through a -3AN or -4AN line.

Common sizes and fittings

Most aftermarket turbo oil feed kits use -3AN or -4AN hose. -3AN has an inside diameter around 0.125 inch and is plenty for a journal bearing turbo with a restrictor. -4AN is around 0.187 inch inside diameter and works for larger journal bearing turbos or engines with lower oil pressure. The oil drain line is a different animal. It runs from the bottom of the turbo back to the oil pan and uses a much larger -8AN or -10AN hose because it relies on gravity instead of pressure.

• PTFE braided stainless: best all-around choice, oil resistant, heat resistant, no rubber contamination.
• Hard steel or stainless line: OEM style, reliable but less flexible, needs good routing and support.

Oil-rated hydraulic hose can work if it is rated for hot oil and high pressure, but it is bulkier and less common in aftermarket turbo kits than PTFE braided hose.

Restrictors and install details

Ball bearing turbochargers often need a small restrictor in the oil feed fitting to limit oil volume. Journal bearing turbos typically need full unrestricted flow. Always use the restrictor size recommended by the turbo manufacturer. A feed line that dumps too much oil into the center housing can push oil past the turbine and compressor seals, producing smoke at idle or under boost. Too little oil kills the bearings.

Route the feed line away from the exhaust manifold and turbine housing. If clearance is tight, wrap the hose or use a fire sleeve. Use a quality PTFE-compatible AN fitting. Because PTFE hose uses a different ferrule than rubber-lined braided hose, the ferrule and olive must match the hose brand, or the fitting will leak under pressure and heat.

Which hose goes on the car?

The hose to order for a turbo oil feed is a -3AN or -4AN PTFE stainless steel braided hose with AN fittings and the correct restrictor, or the factory hard line if you're keeping the stock turbo. Never use silicone, heater hose, or non-oil-rated rubber. Check the drain line for kinks and the fittings for cracks before you install the new feed line. Replace the copper washers or gasket at the banjo fitting every time. If your turbo has a restrictor, verify it's clean before you start the engine.

If you're also replacing vacuum and coolant lines near the turbo, that's where a high-temp silicone hose and proper heat-shrink clamps, like Hose Candy's silicone line and Boa Clamps, earn their keep. For the oil feed itself, keep it oil-rated PTFE and stainless braid.