AMSOIL 5W-40 100% Synthetic Metric Motorcycle Oil

AMSOIL 5W-40 100% Synthetic Metric Motorcycle Oil

Designed for Four-Stroke Metric Motorcycles

AMSOIL 5W-40 Synthetic Metric Motorcycle Oil is engineered for sport bikes, cruisers, touring, and adventure motorcycles.
It provides superior lubrication for both engines and transmissions.
Fully wet-clutch compatible to ensure smooth, reliable gear changes and confident riding.

Exceptional Protection Against Heat and Wear

Superior High-Temperature Film Strength

This oil surpasses industry benchmarks for film strength at elevated temperatures, ensuring robust wear protection.

Powerful Anti-Wear Additives

Formulated with a heavy dose of anti-wear agents, it minimizes engine wear in all riding conditions.
Its advanced chemistry resists volatility and prevents sludge buildup and carbon deposits.

Clutch Performance and Smooth Shifting

Friction Modifier Free Formula

Free from friction modifiers, it supports seamless clutch engagement and shifting.
Specifically designed to control heat and reduce clutch slippage and glazing.

Extended Clutch Durability

Helps maintain clutch health for longer life under rigorous riding scenarios.

Effective Foam Control for Reliable Lubrication

Incorporates cutting-edge anti-foam additives to prevent oil foaming during high-RPM conditions.
Ensures steady oil film and wear protection so riders can push their motorcycles with confidence.

Additional Information

For complete specifications, please consult the product data sheet.

AMSOIL 5W-40 100% Synthetic Metric Motorcycle Oil

AMSOIL 5W-40 100% Synthetic Metric Motorcycle Oil is built for modern four-stroke metric motorcycles that get used the way they were meant to be used—hard, often, and in all kinds of weather.

It’s designed for:

• Sport bikes
• Cruisers
• Touring bikes
• Adventure motorcycles

The formula lubricates both the engine and transmission in shared-sump designs and is fully wet-clutch compatible, so you get confident shifting and predictable clutch feel every ride. This 5W-40 grade holds a strong 4.9-star rating, with reviews credited to AMSOIL.com.

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Designed For Real-World Metric Riding

Wide Operating Range For Varying Conditions

5W-40 is a very versatile viscosity for metric motorcycles:

• The “5W” side flows quickly at cold start, even on chilly mornings.
• The “40” side provides a strong protective film when your engine is fully hot.

That makes this oil an excellent choice if you ride in:

• Cool mornings and hot afternoons
• City traffic during the week
• Longer, higher-speed runs on weekends

It’s especially well-suited for riders who see a mix of stop-and-go, highway and spirited riding on the same bike.

Engineered For Shared Sump Systems

Most metric motorcycles use one oil for:

• Engine internals
• Transmission gears
• Wet clutch pack

AMSOIL 5W-40 Synthetic Metric Motorcycle Oil is formulated specifically for that environment. It is not a repurposed automotive oil. The base oils and additives are tuned so the same fluid can:

• Protect bearings and rings
• Cushion high-load gear contact
• Deliver the right friction behavior for wet clutches

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Exceptional Protection Against Heat And Wear

Superior High-Temperature Film Strength

High-revving engines, tight fairings and heavy traffic all create heat. This oil is built with superior film strength at elevated temperatures, so it can hold a protective layer between metal surfaces when the engine is fully worked.

That strong film helps protect:

• Cam lobes and followers
• Main and rod bearings
• Piston skirts and cylinder walls
• Transmission gears under load

Even during aggressive riding or fully loaded touring, the oil maintains a stable protective barrier instead of thinning out.

Powerful Anti-Wear Additive System

AMSOIL loads this 5W-40 with heavy-duty anti-wear additives. Those additives react under pressure to form a protective layer on critical metal surfaces.

They help:

• Reduce metal-to-metal contact during high-load events
• Minimize long-term wear in engines that see frequent high RPM
• Support smooth operation as mileage adds up

Whether you’re commuting daily, carving back roads or taking multi-day trips, the anti-wear chemistry is working quietly in the background to protect your investment.

Resists Volatility, Sludge And Carbon

Cheap oils can evaporate and leave behind thick residues and deposits. This 5W-40 uses thermally stable synthetic base stocks and modern additive chemistry to resist:

• Volatility and oil consumption
• Sludge formation in low-flow areas
• Carbon deposits on pistons and in ring grooves

The result is cleaner internals and more consistent performance. Your engine doesn’t have to fight its own deposits just to make power.

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Clutch Performance And Smooth Shifting

Friction Modifier-Free For Wet Clutches

Automotive “energy conserving” oils often contain friction modifiers that can cause motorcycle clutches to slip. AMSOIL 5W-40 Metric Motorcycle Oil contains no friction modifiers.

By leaving those out and tuning the base chemistry carefully, this oil:

• Promotes positive clutch engagement
• Helps prevent clutch slippage under hard acceleration
• Reduces the risk of glazing on clutch plates

You get a clutch that grabs when you ask and remains predictable as the ride goes on.

Reduced Slippage, Glazing And Heat

Heat is the enemy of clutch life. When a clutch slips excessively, it creates more heat, which can lead to:

• Plate glazing
• Hot spots
• A vague or inconsistent engagement point

This oil is specifically designed to control heat at the clutch interface and support a consistent friction profile. That helps:

• Prevent chronic slippage
• Minimize glazing during aggressive use
• Extend clutch life in demanding conditions

Smooth, Confident Gear Changes

Because the engine and gearbox share the same oil, transmission feel depends directly on oil quality. The shear-stable 5W-40 viscosity and tailored additives help:

• Cushion gear engagement
• Reduce notchiness as the oil ages
• Maintain a solid, predictable shift feel across the service interval

You get clean, positive shifts whether you’re short-shifting in town or running close to redline on an open stretch.

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Foam Control For High-RPM Riding

Why Foam Is A Problem

At high RPM, spinning shafts and meshing gears can whip oil into a froth. Foam contains air pockets instead of solid oil, which can:

• Reduce effective lubrication
• Disturb oil pressure
• Increase wear if left unchecked

Advanced Anti-Foam Additives

This 5W-40 incorporates cutting-edge anti-foam additives that help keep air bubbles under control. That means:

• A more stable oil film on bearings and gears
• More consistent oil pressure at high RPM
• Reliable lubrication when you’re pushing the bike hard

If you ride aggressively, do long highway runs or track days, consistent lubrication under high RPM is a big confidence booster.

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Engine Cleanliness And Corrosion Protection

Keeping The Inside Of Your Engine Clean

The detergent and dispersant package in this oil is designed to:

• Keep combustion by-products suspended in the oil
• Help prevent deposit formation on hot surfaces
• Keep ring packs and oil passages cleaner over time

Cleaner internals will help:

• Maintain compression
• Support efficient combustion
• Make long-term ownership less stressful and more predictable

Protection During Storage And Bad Weather

Between rides, moisture and acids can slowly attack unprotected metal surfaces. The corrosion-inhibiting additives in this 5W-40 help:

• Guard against rust on critical internal parts
• Neutralize acids formed from combustion
• Protect the engine during short-term storage or seasonal downtime

Change to fresh oil before longer storage and the engine sits in a protective bath instead of dirty, acidic fluid.

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When To Choose 5W-40 In The Metric Lineup

AMSOIL’s Metric Motorcycle oils come in several viscosities (like 10W-30, 10W-40, 5W-40, 15W-50).

5W-40 is an excellent choice if:

• Your manual allows or recommends 5W-40
• You ride in a wide range of temperatures, including colder starts
• You want stronger high-temperature protection than a 10W-30, but quicker cold flow than a thicker 15W-50
• You mix city, highway and aggressive rides on the same bike

Always verify the recommended viscosities and specifications in your owner’s manual, then match them with the grade that best fits your climate and riding style.

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AMSOIL Motorcycle Octane Boost – Ideal Partner For Metric Engines

What Octane Boost Does

AMSOIL Motorcycle Octane Boost is designed to raise the effective octane of your fuel by up to three numbers when treated at the recommended rate.

Higher octane can help:

• Reduce engine knock or ping
• Support more efficient combustion
• Improve throttle response, especially at low RPM

It’s especially useful if:

• You’re forced to use lower-quality fuel
• You ride in hot weather under heavy load
• Your engine is sensitive to spark knock at certain RPM ranges

Knock Control And Low-RPM Smoothness

Engine knock (detonation) can sap power and, over time, damage components. Modern ECUs compensate by pulling timing, which reduces performance.

By boosting octane, this additive:

• Makes knock less likely under load
• Reduces how often the ECU has to cut timing
• Helps maintain strong, smooth low-RPM power delivery

You feel this as cleaner acceleration and less rattling or pinging when rolling on the throttle.

Cleaning Combustion Chambers And Fuel Systems

Octane Boost isn’t just about knock. It also includes detergent chemistry that:

• Helps clean combustion chambers
• Keeps injector tips and fuel pathways cleaner
• Supports more efficient, consistent combustion over time

Cleaner chambers and fuel systems can lead to:

• Better throttle response
• Smoother idle
• More consistent fuel economy

For riders who want even more cleaning, AMSOIL also recommends using a dedicated fuel-system cleaner like AMSOIL Quickshot® alongside Octane Boost as part of a regular maintenance routine.

Compatibility And Emissions Safety

At the recommended treat rate, AMSOIL Motorcycle Octane Boost is:

• Safe for catalytic converters and oxygen sensors
• Compatible with other AMSOIL fuel additives
• Suitable for motorcycles equipped with modern emission control systems

That means you can enjoy the extra protection and performance without worrying about damaging sensitive exhaust components.

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Putting It Together: Oil + Octane Boost For Metric Performance

When you combine AMSOIL 5W-40 100% Synthetic Metric Motorcycle Oil with AMSOIL Motorcycle Octane Boost, you’re covering two of the biggest needs of a modern metric motorcycle:

• Premium lubrication for the engine, transmission and clutch
• Controlled combustion with reduced knock and cleaner fuel delivery

The oil delivers:

• Strong high-temperature film strength
• Powerful anti-wear protection
• Stable clutch behavior and smooth shifting
• Foam control and long-term cleanliness

Octane Boost delivers:

• Higher effective octane
• Less knock and smoother low-RPM performance
• Cleaner combustion chambers and fuel pathways

Together, they help your metric motorcycle run smoother, stay cleaner and feel stronger, whether you’re commuting, touring, carving back roads or exploring new routes on the weekend.