Lubricant Base Oils Group I: Market Size & Forecast 2026

The global lubricant base oils Group I market reaches approximately USD 6.0 billion in 2025 (base year), operating in a structurally declining state amid rapid substitution by higher-quality Groups II and III base oils. The category faces dual pressure from regulatory inflection and feedstock economics, with Group I representing a legacy segment losing ground in all major end-use markets despite its cost advantages in specific applications. > **Analyst Take.** Our view: the 1 October 2026 API SP/GF-7 implementation is the most under-appreciated inflection. Buyers anchored to current Group I supply contracts face 15-20% step-up costs as producers rationalize legacy capacity. Lock indexed structures now with mechanisms to flip to Group II pricing upon standard implementation; resist supplier requests to extend fixed-price 2027 cover beyond Q3 2026.

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