🔬 The Lubricant Lab: Sequence IVB Valvetrain Wear Test—Methodology & Advances Over IVA 🛠️
The Sequence IVB test (ASTM D8350) measures how well engine oils protect modern overhead-cam valvetrains. Developed for ILSAC GF-6 and API SP, it replaces Sequence IVA, with test conditions that better reflect real-world stop‐and‐go driving.
Test Setup & Conditions
🔹 Engine Platform: A 2011 Toyota 2NR‐FE 1.5L inline‐4 with dual overhead cams and direct-acting bucket tappets (16 lifters). This modern design features higher spring pressures and more intense metal contact.
🔹 Operating Cycle: The test runs for 200 hours over ~24,000 cycles (30 sec each). The engine alternates between 800 rpm idle and 4300 rpm high-speed, with coolant and oil temperatures maintained around 50°C.
🔹 Wear Measurements: After testing, each lifter’s volume loss is measured using 3D optical profilometry. To pass API SP, average intake lifter wear must not exceed ~2.7 mm³ and iron in the used oil must remain ≤400 ppm.
Why Valvetrain Wear Matters
💥 Extreme Pressures: Cam lobes and lifters collide thousands of times per minute.
⚙️ Boundary Lubrication: Cooler oil films mean more metal-on-metal contact.
⏳ Extended Durability: With longer oil drain intervals, effective wear control is essential.
Advancements Over Sequence IVA
✔ Modern Hardware: IVA used a 1990s Nissan KA24E with rocker followers; IVB employs a Toyota engine with direct-acting tappets, mirroring today’s designs.
✔ Dynamic Cycling: IVA primarily ran at low speed over 100 hours, while IVB doubles the test duration and increases engine speed to 4300 rpm, adding more acceleration stress.
✔ 3D Wear Volume: Instead of merely measuring wear depth in microns, IVB quantifies total material loss (mm³) and monitors iron in the oil for a comprehensive wear assessment.
✔ Higher Stringency: Tighter pass/fail limits demand superior additive chemistry and higher base oil quality—oils that barely passed IVA may fail IVB unless reformulated.
Formulation Factors for Passing IVB
🛡 Anti-Wear Agents (e.g., ZDDP): Form sacrificial phosphate layers protecting surfaces under low-temp, high-load conditions.
🧪 Detergent & Dispersant Synergy: Metallic detergents keep surfaces clean and neutralise acids, while dispersants suspend particles; both must be balanced to support ZDDP’s protective film.
⚙ Friction Modifiers: Ingredients like molybdenum and organic friction reducers lower sliding friction and work with ZDDP to improve wear protection.
Conclusion
Sequence IVB, with its modern hardware, dynamic cycling and precise 3D wear analysis, offers a more rigorous and realistic test than IVA. It ensures that API SP (and GF-6) oils provide robust wear protection under demanding valvetrain conditions.
At Valorem Chemicals, we develop advanced additive packages designed to excel under IVB’s stringent requirements—helping engines run cleaner, longer, and more efficiently.