Clean Pistons: Signature Series and the Sequence IIIH Test

Heat, load and time are relentless. Whether you’re pushing a high-performance vehicle to its limits, venturing deep into the backcountry or towing through steep mountain passes, your engine is constantly under stress. Today’s engines generate more power than ever while operating with tighter tolerances and higher temperatures, placing unprecedented demands on motor oil. For drivers who demand maximum performance, reliability and long-term protection, engine cleanliness is essential. This is especially true with pistons, where deposits can rob power, reduce efficiency and accelerate wear. To see how well it protects against these challenges, we put the new AMSOIL Signature Series 100% Synthetic Motor Oil formulation through one of the industry’s toughest performance tests: Sequence IIIH.

A Harsh Standard

Engine deposits can form when oil breaks down under high heat, leaving harmful buildup on pistons that reduces efficiency and performance. AMSOIL Signature Series 100% Synthetic Motor Oil is formulated to resist thermal breakdown and actively fight deposit formation, helping keep critical engine components clean and operating at peak performance.

The Sequence IIIH test (ASTM D8111) is a fired-engine dyno test used to evaluate the thermal and oxidative stability of engine oil. In the test, a 2012 Chrysler* Pentastar* 3.6L V6 engine is run at a lubricant temperature of 304°F (151°C), rpm of 3,900 and brake horsepower (bhp) of 137. Think of it like simulating driving a fully loaded pickup towing a heavy trailer up a long mountain grade in the desert for 3,000 miles (4,828 km) without a break. The industry-standard test evaluates motor oil in several key performance area and it must be passed to meet API and ILSAC specifications.

Results in the Sequence IIIH test are a good indicator of how well an oil will perform in the real world. It is common for motor oils to barely pass the test with minimum passing scores. After the test, the engine is torn down and the pistons are examined. They receive a score based on weighted piston deposits. The higher the score, the cleaner the oil kept the pistons.

Industry-Leading Cleanliness

Signature Series is barely challenged by Sequence IIIH. The new Signature Series formulation delivered outstanding results in the test, providing 72% more protection against piston deposit formation than industry standards.¹

The new Signature Series formulation received the highest rating ever achieved at the lab that performed the test – and that lab performs testing for many different motor-oil brands.

Doubling Down

To further challenge the formulation, AMSOIL asked the third-party lab to double the length of the test, and Signature Series continued to outperform expectations. Even after doubling the Sequence IIIH test, Signature Series delivered cleaner pistons than required by the industry standard – providing 31% better protection than required.²

Next-Level Protection

The Sequence IIIH test is designed to push motor oil to its limits, replicating harsh operating conditions. In this demanding environment, AMSOIL Signature Series 100% Synthetic Motor Oil delivered exceptional piston cleanliness. Results from the Sequence IIIH prove that Signature Series doesn’t simply meet industry standards — it surpasses them by a significant margin. For enthusiasts, truck owners and anyone who demands maximum protection under severe operating conditions, AMSOIL Signature Series delivers the cleanliness, performance and protection needed to help keep engines running at their best for miles to come.

¹Based on AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil results in the Sequence IIIH test.
²Based on AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil results in a double-length Sequence IIIH test.