No Sludge. Just Protection.

Engines today work harder than ever. Higher temperatures, increased power density and demanding operating conditions put motor oil under constant stress. Add in frequent towing, stop-and-go driving, long highway miles or extreme temperatures, and oil must work overtime to protect critical engine components.

As motor oil ages, its ability to combat heat, oxidation and contamination becomes increasingly important. When oil breaks down, harmful deposits can form and threaten engine performance. That’s why AMSOIL Signature Series 100% Synthetic Motor Oil is engineered to resist breakdown, maintain cleanliness and deliver lasting protection over extended drain intervals.

The Black Death

Sludge is the arch nemesis of an engine. Formed when oil degrades and contaminants accumulate, sludge creates thick, sticky deposits that can settle throughout the engine. These deposits can clog oil passages and screens, foul sensors and interfere with the precise operation of critical engine components. As sludge builds, oil circulation becomes less efficient, causing increased friction, elevated operating temperatures and reduced performance. In severe cases, sludge can block the flow of oil to vital components, increasing the risk of costly repairs and shortening engine life. No wonder some mechanics refer to sludge as the “black death.”

Next-Level Protection

AMSOIL Signature Series 100% Synthetic Motor Oil is engineered to resist breakdown and maintain exceptional cleanliness, helping prevent sludge from forming even in extreme conditions. Signature Series helps prevent sludge formation by resisting the heat, oxidation and contamination that can cause motor oils to break down. Its advanced synthetic formulation maintains stability under extreme operating conditions, helping keep critical oil passages clean and ensuring consistent oil flow throughout the engine.

To challenge its abilities to guard against sludge, Signature Series 5W-30 100% Synthetic Motor Oil (ASL) was installed in a 2025 Ford* F-150 Raptor* equipped with a high-output V6 engine and run through a 125,000-mile (201,168-km) test. Oil changes were performed at 25,000-mile (40,234-km) intervals, and power sweeps were performed before and after the 125,000-mile test protocol.

After the test, we analyzed every component to see how they held up under harsh conditions, including the oil screen, one of the first places sludge will appear if it’s present. AMSOIL Signature Series demonstrated outstanding performance over extended use. During the 125,000-mile accumulation study, the engine experienced 0% oil-screen plugging,1 demonstrating its ability to keep engines clean and protected.

Undaunted Performance

The 125,000-mile accumulation study was designed to push motor oil beyond the challenges most drivers encounter. Through sustained high temperatures, heavy loads and extended service intervals, AMSOIL Signature Series maintained its protective properties and kept sludge-causing deposits in check.

The results demonstrate the value of a motor oil engineered for long-term durability. By resisting breakdown and helping prevent sludge formation, Signature Series keeps oil flowing freely where it’s needed, helping protect against wear and supporting long-lasting engine performance. For drivers who expect maximum performance and reliability from their vehicles, Signature Series delivers the cleanliness and protection needed to help keep engines running strong for the long haul.