Since March 31, 2025, a significant change has taken effect in engine oil specifications: the maximum mini-rotary viscometer (MRV) viscosity for ILSAC GF-7 and API SQ dropped from 60,000 cP to 40,000 cP for fresh oil. This 33% reduction in cold-start pumpability limits represents a substantial change with major implications for lubricant blenders.
📋 ILSAC GF-7 has defined this new MRV cap across both subcategories:
- GF-7A: SAE 0W-20, 5W-20, 0W-30, 5W-30, and 10W-30
- GF-7B: SAE 0W-16
📋 API SQ has also imposed the same 40,000 cP ceiling, extending to 0W-12 and 0W-8 under its non-Resource Conserving subset.
🧪 The MRV test (ASTM D4684) simulates oil pumpability after an overnight cold soak, capturing two distinct failure risks:
1️⃣ Apparent Viscosity (cP): This measures how “thick” the oil behaves at cold temperatures—like trying to draw honey through a straw on a winter morning. By reducing the upper limit to 40,000 cP, GF-7 has ensured faster cold flow and quicker pressure buildup during startup.
2️⃣ Yield Stress (Pa): This more critical parameter represents the threshold force needed to make the oil start moving at all. Yield stress indicates gelation from wax crystal networks. Even a low-viscosity oil will fail if any yield stress is detected.
⚠️ In essence:
- High viscosity = slow flow
- Yield stress = no flow
✅ MRV pass criteria now require both viscosity ≤40,000 cP and no measurable yield stress at the grade-specific test temperature.
🧠 For formulators, meeting these targets has required recalibration:
🔹 Base oil quality: Greater use of Group III, PAO, or GTL became necessary 🔹 Pour point depressants: PPD chemistry needed adjustments to prevent wax crystallisation during slow cooling 🔹 Polymer selection: Viscosity modifiers required careful selection to avoid adverse low-temperature behavior 🔹 Testing discipline: Increased reliance on MRV, Gelation Index, and Engine Oil Gelation Test
🚗 For OEMs and end users, the benefits include: 🔹 Faster cold-start lubrication 🔹 Reduced pump starvation risk 🔹 Improved oil pressure reliability 🔹 Better fuel efficiency during warm-up
🏆 While SAE J300 still lists 60,000 cP as the MRV limit for a “W” grade, GF-7 has raised the bar. It now mandates oil that flows immediately and continuously—even at temperatures as low as –35 °C.
🤝 At Valorem Chemicals, we support partners in achieving these tighter targets. Whether sourcing ultra-low pour point base oils or evaluating additive response curves under ASTM D4684, our team brings the technical focus needed to stay ahead of specification.