Don’t Let Extreme Heat Sideline Your Motorcycle

An Oil to Resist Thinning from Extreme Heat and Mechanical Activity

Extreme summer heat combined with slow-moving rally or parade traffic can pose big problems for you and your motorcycle.

As heat intensifies, motor oil loses viscosity and becomes thinner. The oil can become so thin that the engine loses oil pressure, causing the oil-pressure gauge to bottom out. You may hear increased valvetrain and gear noise as parts clatter together. A good rider knows not to ride with no oil pressure, so he or she will shut down the bike and sit alongside the highway (or push the bike) until the engine cools enough to restore oil pressure.

Decreased airflow stresses oil

Air-cooled V-twins get plenty hot on their own, but riding in slow moving traffic makes it worse. Crawling along barely above idle doesn’t generate enough airflow to cool the engine. Add to that the blazing sun reflecting off the asphalt, and it’s a recipe for trouble. In extreme dyno testing designed to create heat, we’ve seen cylinder temperatures in a 2012 Harley-Davidson* Street Bob* as high as 383°F (195°C).

It’s up to the motor oil to protect the engine despite the intense heat; however, oil becomes thinner as it heats up. If it becomes too thin, it can fail to form a lubricant film of enough thickness and strength to prevent metal components from contacting during engine operation and wearing out. Once the lubricant film fails, it falls on the anti-wear additives to prevent wear. They form a sacrificial layer on components to keep them from contacting. But additives are designed to deplete with time and use. Once they wear out, your engine isn’t protected in this scenario.

Heat breaks down oil faster

The rate at which oil oxidizes, or chemically breaks down, doubles for every 18°F (10°C) increase in lubricant temperature. Oxidation occurs when oxygen molecules attack oil molecules and result in a chemical reaction that leads to harmful byproducts, like sludge and varnish. The faster the oil oxidizes, the sooner it wears out and requires changing.

Ride Hard. Run Cool.®

AMSOIL Synthetic V-Twin Motorcycle Oil uses high-quality synthetic base oils that naturally resist thinning due to extreme heat and mechanical activity better than conventional base oils. As a result, it forms a thick, strong lubricating film on engine components despite the intense heat. Although any oil will become thinner in extreme heat, riders who use AMSOIL Synthetic V-Twin Motorcycle Oil won’t see their oil-pressure gauges bottom out, providing the confidence they need to keep riding after others have shut down their bikes and started pushing.

Find AMSOIL Products for My Bike

*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for use in the applications shown.

Where Oil Goes and What it Does

The Responsibilities of Your Motor Oil

A typical engine contains hundreds of parts, none of which could function properly without oil. Far from a simple commodity, oil is a dynamic enabler of performance. It must lubricate, cool, protect, seal, actuate components and more. And it must do it all while exposed to tremendous heat and stress. Here, we highlight key areas where oil goes inside your engine and what it does once it’s there.

Variable Valve Timing (VVT)

To increase fuel economy and reduce emissions, most modern engines use VVT systems to adjust when the valves open and close. VVT systems use motor oil as a hydraulic fluid to actuate cam-phaser components. Solenoids, like the one shown here, control cam-phaser timing. These solenoids contain tiny openings through which the oil must flow. Even minimal varnish or deposits can disrupt the system, triggering a check-engine light. The oil must maintain viscosity to function as a hydraulic fluid while resisting deposits to maximize VVT system performance.

Valves and Seals

Valve seals prevent oil from running down the valve stems. This keeps the oil on valvetrain components and prevents it from entering the intake and exhaust ports and burning, increasing oil consumption. The oil must condition these seals to prevent drying, cracking and leaking. The oil also helps cool the valves and control cylinder-head deposits, helping prevent valve sticking.

Main Seals

The seals at the ends of the crankshaft keep the oil inside the engine. The oil must condition seals to prevent drying, cracking and leaking.

Wrist Pins & Undercrowns

Crankshaft eccentrics splash-lubricate the cylinders, wrist pins and piston undercrowns. Some engines have small nozzles that spray oil directly onto the wrist pins and undercrowns. The rapidly spinning crankshaft causes air entrainment in the oil, creating foam. If foam bubbles in the oil pass between metal parts, they collapse and cause metal-to-metal contact. The oil must contain anti-foam additives to quickly dissipate foam. The oil must also contain detergent additives to help keep the wrist pins and undercrowns clean.

Connecting Rods & Main Bearings

Combustion drives the pistons down the cylinder, creating intense pressure between the connecting rods, main journals and bearings. Oil molecules act like microscopic ball bearings that support this pressure and allow the rods and crankshaft to rotate without metal-to-metal contact. The oil must maintain its protective viscosity despite increased pressures, temperatures and shearing forces. If the fluid film weakens, the oil will squeeze from between the journal and bearing clearances, resulting in metal-to-metal contact and bearing wear.

Camshaft

The camshaft and lifters open and close the intake and exhaust valves. To prevent wear, the oil must form a strong fluid film that separates the cam lobes and lifters. It also must contain robust anti-wear additives to maximize the life of the camshaft and bearings. As the image below shows, AMSOIL Signature Series 0W-20 Synthetic Motor Oil did an excellent job protecting against cam wear in rigorous, third-party testing.

Pistons, Rings & Cylinders

The pistons compress the air in preparation for combustion. The piston rings perform several critical functions: they must seal the combustion chamber, return excess oil on the cylinder walls to the sump and transfer extreme piston-crown heat to the cylinder walls.

To prevent wear despite intense heat and shearing forces, oil must maintain a strong, consistent film between the rings and cylinder walls. It also must prevent deposits that cause ring sticking, increased oil consumption, compression changes and low-speed pre-ignition (LSPI).

Signature Series Synthetic Motor Oil achieved 100 percent protection against LSPI1 in the engine test required by the GM* dexos1® Gen 2 specification – zero occurrences were recorded throughout five consecutive tests.

Oil Galleries & Passages

An engine contains an intricate network of oil galleries and passages that carry oil to components. Passages in the crankshaft, for example, carry pressurized oil to the rod and main bearings, while similar passages in the upper end carry oil to the valvetrain. Oil that thickens in the cold can fail to flow through narrow passages and starve the engine of oil. Sludge, meanwhile, can plug passages and have the same effect. The oil must remain fluid when the temperature drops, and it must prevent sludge.

Oil Pick-Up Tube Screen

The oil pump draws oil through a fine screen and pressurizes it so it can flow through the oil galleries and passages to the bearings and valvetrain. Sludge can plug the screen, starving the engine of oil. Oil that thickens too much to pass through the screen has the same effect. Therefore, oil must remain fluid when cold to pass through the screen and flow throughout the engine at startup (when most wear occurs). The oil also must prevent sludge to keep galleries and passages clean, ensuring maximum oil flow.

Tag: engine