Milwaukee-Eight Oil Change: Step-by-Step Guide

Introduced in 2017, the Milwaukee-Eight is Harley-Davidson's most advanced Big Twin engine to date. With four valves per cylinder, dual counter-balancers, and significantly improved thermal management over the Twin Cam, the M8 is a more refined powerplant — but it still needs proper, regular oil changes to reach its potential lifespan. This guide covers the process for all Milwaukee-Eight variants: the 107, 114, 117, and 131.

Milwaukee-Eight Variants

• Milwaukee-Eight 107 (1746cc) — Base M8, found in Softail and Touring models from 2017. Air-cooled.
• Milwaukee-Eight 114 (1868cc) — Mid-range option with more torque. Available in Softail and Touring. Air-cooled.
• Milwaukee-Eight 117 (1917cc) — CVO-spec engine with higher compression. Air-cooled with oil-cooled cylinder heads (MOCO).
• Milwaukee-Eight 131 (2147cc) — The biggest production Harley engine ever. Found in CVO models and available as a crate engine. Screamin' Eagle spec.

What You'll Need

• 3.5–4 quarts of 20W-50 full synthetic motor oil (Harley Screamin' Eagle Syn3 or equivalent)
• Oil filter — HD part #63798-99A or equivalent aftermarket
• Primary chaincase oil: approximately 32 oz Harley Formula+ or equivalent
• Drain pan, oil filter wrench, funnel
• Torque wrench (drain plug spec: 14–21 ft-lbs)

Engine Oil Drain and Fill

The Milwaukee-Eight engine shares oil between the engine and the oil cooler (on cooled-head variants). Start with a warm engine — 5–10 minutes of idle — to thin the oil and carry contaminants into suspension.

1. Place drain pan under the oil drain plug on the right side of the engine.
2. Remove the drain plug and allow to drain fully — at least 5 minutes. The M8 holds about 3.5 quarts.
3. Remove the oil filter with a filter wrench. Expect some spillage — have rags ready.
4. Lightly oil the new filter gasket with fresh engine oil. Install new filter hand-tight, then 3/4 turn additional.
5. Reinstall drain plug with a new sealing washer. Torque to 14–21 ft-lbs. Do not over-tighten.
6. Add approximately 3.5 quarts of oil through the filler cap on the rocker box. Check level on the dipstick with the bike upright — don't overfill.

Primary Chaincase Service

The primary chaincase on the M8 has its own separate oil supply. The drain plug is on the bottom of the primary cover on the left side.

1. Remove the derby cover (three bolts) to access the primary chain and inspect the chain and shoe.
2. Remove the primary drain plug and drain completely.
3. Check the clutch diaphragm spring and basket while the cover is off — a quick visual inspection can catch wear early.
4. Reinstall drain plug, refill with approximately 32 oz of HD Formula+ or equivalent primary chaincase lubricant.

Transmission Oil

The six-speed transmission in M8 bikes is a separate compartment. It uses the same HD Transmission Lubricant as the Twin Cam.

1. The transmission drain plug is on the bottom of the gearbox housing — right side of the bike, behind the primary cover.
2. Drain fully, reinstall plug with fresh sealing washer.
3. Refill through the inspection port or dipstick tube with approximately 24 oz of transmission lubricant.

Milwaukee-Eight Service Intervals

In Nova Scotia, the extended winter layup season means many bikes spend 5–6 months parked. We always recommend a full oil change at spring startup regardless of the km on the clock — old oil oxidizes and loses its protective properties over winter.

The Milwaukee-Eight is Harley's most refined engine yet. With proper oil service it will reliably deliver 200,000+ km. Our shop in Pictou County handles M8 services daily — book your seasonal service online or give us a call.