The SPOOLOGIC Turbo Upper Oil Drain Line SL-350-033 is a direct-replacement oil drain line for 6.6L Duramax L5P/L5D (2017-2026) applications. Built to OE form and fit, it returns engine oil from the turbo bearing housing down to the lower drain section. Ships complete with the sealing hardware required to complete the install in one job. Backed by a 1-Year Limited Warranty.

Why You Replace the Drain Line — Not Just the Seals

Oil lines and their sealing hardware are not designed to be reused forever. Here’s what’s actually happening to the parts you’re tempted to put back:

• OE oil drain lines back up. The drain line returns engine oil from the turbo bearing housing to the pan. As the inside coats with baked-on oil coking, flow slows — and the moment the drain restricts, oil backs up in the turbo center section and forces past the seals into the exhaust and intake.
• Rubber flex sections harden and crack. Any flexible section on an OE drain line sees oil at bearing-return temp and the vibration of the engine forever. Eventually the rubber goes brittle, cracks, and the truck starts leaving a puddle on the driveway.
• Flange gaskets and O-rings are single-use. The seals that connect the drain to the turbo and the pan take a permanent compression set the moment they’re torqued down. Reused seals weep engine oil.
• Mounting hardware corrodes and seizes. Drain-line bolts live in the hottest, wettest part of the engine bay. Fresh hardware torques predictably and comes off cleanly the next time the turbo has to come out.

Component Breakdown — What Each Piece Does

• 1 turbo upper oil drain line — formed steel drain line to OE geometry, upper section of the two-piece L5P/L5D drain path.
• Flange gasket — seals the upper drain to the turbo bearing housing.
• Mounting hardware — heat-treated bolts that torque the drain flange down.

Material Technology — Why Each Material Was Chosen

• Formed steel line body — the line is bent to OE geometry so it clears the surrounding components and drops into the factory brackets without modification.
• OE-spec sealing hardware — the included crush washers, O-rings, or gaskets are the correct material and durometer for the oil temperatures and pressures this line sees in service.
• Heat-treated steel bolts and fittings — every threaded fastener in the kit is the correct grade, length, and thread pitch for the port it goes into.

Install Notes

• Clean the turbo-side and pan-side mating surfaces with a plastic scraper and a lint-free rag before installing the new drain line. Old gasket residue, coked oil, or scale will keep the new seals from sealing.
• Install the new gasket and O-rings dry — no RTV, no thread sealant on the gasket face. The seals are designed to seal on clean, flat metal.
• Start all bolts by hand before torquing anything, so the drain line self-aligns without stress on the flanges.
• Follow the OE service manual torque specs in the correct sequence. Over-torque cracks the flanges; under-torque leaks.
• Route the line through the factory brackets and clips — the tubing was bent to clear specific components. Skipping the brackets lets the line rub through under vibration.
• Inspect for oil leaks after a full heat cycle — run the truck to operating temp, shut it down, and check the drain path once cool.

What’s Included

• 1 turbo upper oil drain line
• Flange gasket
• Mounting bolts

Interchange / Cross-Reference

• GM OEM 12720306 — cross-reference
• GM OEM 12737099 — cross-reference

Features

• Direct-replacement oil drain line for 6.6L Duramax L5P/L5D (2017-2026) applications
• Ships with the sealing hardware required to complete the install
• OE form and fit — direct replacement, no modifications
• Backed by a 1-Year Limited Warranty

Fits 2017-2026 6.6L Duramax

• 2017 – 2026 Chevrolet Silverado GMC Sierra 2500 3500 6.6L Duramax L5P
• 2019 – 2026 Chevrolet Silverado 4500 5500 6500 6.6L Duramax L5D

1-Year Limited Warranty

Every SPOOLOGIC turbo oil line is covered by a 1-Year Limited Warranty against defects in materials and workmanship from the date of purchase. Warranty covers replacement of the part only. Warranty does not cover labor, towing, downtime, consequential damages, failures caused by improper installation, failures caused by dirty or damaged mating surfaces, reuse of any included gasket, O-ring, or crush washer, or use outside the listed fitment.