What are the 3 holes on a Harley-Davidson oil change?

Unlike Japanese motorcycles that share a single oil sump for engine, clutch, and transmission, Harley-Davidson Big Twin motorcycles feature three independent oil compartments: (1) Engine Crankcase Sump, (2) Primary Chaincase, and (3) Transmission Gearbox. Each compartment requires specific fluid capacities, viscosities, and dedicated drain plug servicing.

What size O-ring does a Harley-Davidson drain plug use?

Harley-Davidson Big Twins (Twin Cam and Milwaukee-Eight) use OEM Part Number 11105 for all three magnetic drain plugs (Engine, Primary, and Transmission). It is an industry standard -013 size Viton fluorocarbon O-ring measuring 7/16-inch inside diameter (ID), 9/16-inch outside diameter (OD), and 1/16-inch cross-section width.

Can I use the same oil in all 3 holes on my Harley?

While some full-synthetic 20W-50 motorcycle oils (such as Screamin' Eagle SYN3 or Mobil 1 V-Twin) are certified for all three cavities, professional powertrain builders recommend dedicated fluids: 20W-50 Full Synthetic in the Engine Sump, specialized primary fluid or non-friction-modified 80W-90 (Formula+) in the Primary Chaincase to prevent wet clutch slippage, and heavy 75W-140 Full Synthetic Gear Oil in the 6-Speed Transmission to cushion gear dogs and eliminate gear whine.

V-Twin Powertrain Workshop Tool

Harley-Davidson 3-Hole Oil Capacity & Viscosity Calculator

Select your Harley-Davidson powertrain family to calculate exact factory fluid volumes for all 3 separate holes: Engine Crankcase Sump, Primary Chaincase, and Transmission Gearbox. Includes factory drain plug torques, O-ring dimensions, and filter specifications.

Select Harley-Davidson Powertrain Family

Factory specifications calibrate according to engine generation and chassis architecture.

Chamber 1 of 3

Engine Crankcase

4.5 US qt

RECOMMENDED VISCOSITY20W-50 V-Twin Full Synthetic

DRAIN SOCKET5/8" Socket or 1/4" Allen

DRAIN TORQUE14 – 21 ft-lb (19.0 – 28.5 Nm)

DRAIN O-RINGOEM 11105 (Viton -013)

OIL FILTER SPECHiFloFiltro HF171B (Black) / HF171C (Chrome)

Workshop Tip: Do not overfill past middle of dipstick crosshatch on jiffy stand to prevent blow-by oil misting into air cleaner.

Chamber 2 of 3

Primary Chaincase

30 fl oz

RECOMMENDED FLUIDHarley-Davidson Formula+ or Synthetic Primary Lube (80W-90)

DERBY COVER BOLTS5x T27 Torx bolts in star pattern

DERBY TORQUE84 – 108 in-lb (9.5 – 12.2 Nm)

GASKET PARTOEM 25416-99C (Flat disc rubber gasket)

FLUID LEVEL CHECKWith bike upright, fluid touches bottom of clutch diaphragm spring

Clutch Friction Warning: Strictly avoid passenger car oils with friction modifiers (molybdenum) to prevent clutch slip.

Chamber 3 of 3

Transmission Gearbox

28 fl oz

TRANSMISSION ARCHITECTURE6-Speed Cruise Drive

RECOMMENDED GEAR LUBE75W-140 Full Synthetic Heavy Gear Lube

DRAIN PLUG TORQUE14 – 21 ft-lb (19.0 – 28.5 Nm)

DIPSTICK INSPECTION RULERest dipstick threads on case without screwing down (upright position)

Gear Protection: Heavy synthetic 75W-140 cushions helical gear teeth and reduces 5th gear highway whine.

Direct Workshop Cart Manifest

Required Service Consumables for Milwaukee-Eight (M8) Touring (2017–Present)

Shop Harley Oils & Filters →

ENGINE MOTOR OIL5 Quarts20W-50 V-Twin Full Synthetic

PRIMARY CHAINCASE1 QuartHarley Formula+ or 80W-90 Primary

TRANSMISSION GEAR LUBE1 Quart75W-140 Full Synthetic Gear Oil

HARDWARE & SEALS3x O-Rings + 1x FilterOEM 11105 Viton + HF171B Filter

Harley-Davidson 3-Hole Oil Service Engineering Manual

1. Engine Sump vs. Flywheel Cavity

Harley Big Twins use a dry-sump lubrication system where oil is held in an external pan beneath the transmission. When draining, always elevate the motorcycle on its jiffy stand and allow at least 10 minutes for oil to evacuate the lower passages. Always pre-fill the oil filter 1/3 full with fresh 20W-50 to eliminate dry bearing startup scuffing.

2. Wet Clutch Friction Chemistry

The primary chaincase shares fluid between the engine compensator, double-row chain, and multi-plate wet clutch. Standard automotive motor oils contain energy-conserving friction modifiers (molybdenum) that glaze wet clutch friction discs. Use only JASO MA2 or dedicated primary fluid (Formula+ or 80W-90).

3. Transmission Helical Gear Shear Protection

The Harley 6-Speed Cruise Drive transmission uses straight-cut 1st and helical 2nd through 6th gears. Under heavy torque, helical cut teeth generate immense axial thrust and sliding shear. Heavy 75W-140 full-synthetic gear oil maintains high film strength under extreme pressure (EP) to eliminate 5th gear whine.

Read the Full In-Depth Workshop Guide

Step-by-step photos, T27 derby cover sequence, and dipstick cold vs hot levels.

Read 3-Hole Manual →