From Solvent Refining to Wax Isomerization: How Group III and Group III+ Base Oils Became the Global Standard for High-Performance Lubricants

The API Base Oil Classification System: Why It Matters to Buyers

When procurement managers and lubricant formulators specify base oil, the API group classification is the first filter. Introduced in 1993 under API 1509, the five-group system was created to standardise base oil quality across a fragmented global supply chain. Three parameters define the classification: saturates content, sulphur content, and viscosity index.

The distinction between Group III and Group III+ is not an official API category — it is a market-driven designation that emerged as OEM specifications pushed viscosity index requirements beyond what standard Group III could reliably deliver. Today, Group III+ with VI ≥ 130 is the de facto requirement for formulating 0W-16 and 0W-20 engine oils meeting the latest ILSAC and ACEA standards.

Section 1 — The Group I Era: Sufficient, But Not Future-Proof (1950s–1980s)

Group I base oils dominated global lubricant formulation for most of the twentieth century. Produced through solvent refining — a process combining furfural extraction, solvent dewaxing and hydrofinishing — Group I oils offered acceptable performance for the engine technology and drain interval expectations of the era.

The typical product range: SN150, SN500 and Bright Stock. Sulphur content above 0.03 percent. Saturates below 90 percent. Viscosity index ranging from 80 to 120 depending on crude origin and processing severity.

For 1970s and 1980s engines operating on 5,000 to 10,000 kilometre drain intervals, this was sufficient. The lubricant's job was primarily to reduce friction and suspend contaminants — not to survive 15,000 kilometre drain cycles at temperatures exceeding 150°C.

The first structural pressure on Group I came from the United States. The Corporate Average Fuel Economy (CAFE) standards introduced in 1975 pushed automakers to reduce vehicle weight and improve engine efficiency. Thinner, cleaner lubricants became part of the fuel economy equation. Group I's high sulphur content and lower oxidation stability began to look like a liability.

Section 2 — The Hydrocracking Transition: How Group II Redrew the Supply Map (1980s–2000s)

Hydrocracking replaces the solvent extraction step with hydrogen treatment at high pressure and temperature. The result: sulphur content drops below 0.03 percent, saturates rise above 90 percent, and the base oil is significantly more oxidation-stable than its Group I equivalent.

Japan was the first major market to drive Group II adoption at scale. Toyota and Honda, targeting export markets with strict emissions requirements, began specifying longer drain intervals and tighter lubricant performance standards through the JASO engine oil standards. Japanese refiners responded with hydrocracking investment through the 1980s and 1990s.

Korea moved faster and more aggressively. SK Lubricants — now SK Enmove — made a strategic decision in the late 1990s to build large-scale Group II and Group III hydrocracking capacity. GS Caltex followed. Within a decade, Korea had repositioned itself as Asia's dominant base oil exporter, with Group II and Group III products reaching lubricant blenders across Southeast Asia, South Asia and beyond.

The API specification upgrades reinforced this transition. API SH in 1993, API SJ in 1997, API SL in 2001 — each successive category tightened oxidation stability, sludge resistance and volatility requirements. Group I could meet early categories with additives but struggled to keep pace as the standards tightened.

Section 3 — The Regulatory Push That Created Group III Demand

Group III base oil did not emerge because refiners decided to invest in better technology. It emerged because regulators, automakers and OEMs created a market that required it.

The European Union's role was decisive

The EURO emission standards — EURO III in 2000, EURO IV in 2005, EURO V in 2008, EURO VI in 2013 — systematically tightened exhaust emission limits across the EU. Each upgrade required engines to run cleaner and longer between service intervals. The ACEA lubricant specifications tracked this progression: ACEA A3/B4 required viscosity index above 120. ACEA C3 and C5 pushed low-SAPS (sulphated ash, phosphorus, sulphur) formulations that demanded high-purity base oils to minimise ash contribution. Group I was effectively excluded from premium European lubricant formulations by the mid-2000s.

The United States ILSAC programme drove volatility requirements

ILSAC GF-3 in 2001 introduced Noack evaporation limits for the first time — no more than 15 percent mass loss at 250°C. ILSAC GF-4 in 2004 tightened this to 13 percent and introduced phosphorus limits to protect catalytic converters. ILSAC GF-5 in 2010 made fuel economy improvement a quantified requirement, accelerating the shift to 0W-20 as the volume grade in the North American market. Each step pushed base oil viscosity index requirements upward and Group III adoption accelerated.

China's transition created the largest single demand signal

China's emission standard progression — Guojia IV in 2010, Guojia V in 2017, Guojia VI in 2020 with full GB6b implementation in 2023 — brought Chinese engine oil requirements to near-European levels within fifteen years. China is the world's largest lubricant market, consuming approximately seven million tonnes annually. The domestic Group III production base was insufficient to meet the pace of demand growth. Import volumes from Korea, the Middle East and later from domestic producers including Sinolook increased sharply through the 2010s and into the 2020s.

The Middle East made a strategic refinery investment decision

ADNOC in Abu Dhabi positioned base oil upgrading as a core pillar of its downstream diversification strategy. BAPCO in Bahrain expanded Group III capacity at its Bapco Refining facility. Saudi Aramco's joint venture base oil operations moved progressively toward Group II and Group III output. The Middle East shifted from a Group I-dominant supply region to a significant Group III exporter within a decade — before the Strait of Hormuz supply disruption of early 2026 introduced new freight and supply continuity risk for buyers dependent on Gulf origin cargoes.

Section 4 — Group III+: When the Market Outpaced the Standard

The API classification system has five groups. Group III+ is not one of them.

The designation emerged organically as lubricant formulators encountered a practical problem: 0W-16 and 0W-20 engine oils meeting ILSAC GF-6 and GM dexos1 Gen. 3 requirements needed base oils with viscosity index above 130 and cold crank simulator viscosity at -35°C below levels that standard Group III could consistently achieve.

ILSAC GF-6, introduced in 2020, created two sub-categories: GF-6A for existing viscosity grades and GF-6B specifically for 0W-16. The 0W-16 grade requires extremely low low-temperature viscosity — a specification that effectively mandates Group III+ as the base stock. Standard Group III with VI between 120 and 129 can be formulated into 0W-20 with careful additive selection, but 0W-16 is significantly more demanding.

GM dexos1 Gen. 3, released in 2022, formalised this in OEM terms. The specification requires base oils with viscosity index of 130 or above for approved formulations — making Group III+ not just preferred but required for dexos1 Gen. 3 compliance.

ACEA 2023 continued this trajectory. The C5 and C6 categories, designed for the latest generation of fuel-efficient European engines, set low-temperature and volatility requirements that functionally require Group III+ input.

The result is a two-tier Group III market. Standard Group III — VI 120 to 129 — remains the workhorse for 5W-30, 5W-40 and 10W-40 formulations across the mainstream lubricant market. Group III+ — VI 130 and above — has become the required input for the fastest-growing segment: ultra-low viscosity engine oils for modern fuel-efficient powertrains.

Section 5 — The 2026 Supply Disruption and What It Revealed

The Strait of Hormuz disruption beginning in February 2026 stress-tested the global Group III supply chain in real time.

Middle East origin Group III — from ADNOC, BAPCO and Saudi Aramco joint ventures — accounts for a significant share of supply to European and Asian markets. When force majeure declarations began flowing from Gulf-origin suppliers in late February and March 2026, buyers without diversified supply arrangements faced immediate allocation problems. Group III prices in northern Europe rose approximately 100 percent from Q1 2026 levels. Spot availability tightened sharply.

The disruption exposed a structural vulnerability that procurement managers had largely ignored during years of stable Gulf supply: single-origin dependency in a commodity where supply continuity is as important as specification compliance.

Malaysia-origin supply was unaffected. The Malacca Strait remained open. Port Klang continued operating on normal schedules. Buyers with Malaysia-origin supply arrangements maintained uninterrupted availability through the disruption period.

This is not a temporary advantage. The geopolitical risk premium on Middle East origin petroleum products has structurally increased. Buyers building supply chain resilience are actively seeking to diversify origin, and Malaysia — with direct liner services to Vietnam, Indonesia, Bangladesh, India, Sri Lanka and the Middle East — is well positioned as a secondary or primary supply origin for Asian buyers.

Section 6 — ILSAC GF-7 and API SQ: The Next Transition Is Already Underway

ILSAC GF-7 is the next major specification upgrade for passenger car motor oils in the North American market. While final publication timing remains subject to industry alignment, the direction of travel is clear: tighter fuel economy requirements, enhanced low-speed pre-ignition (LSPI) protection, and further tightening of volatility and low-temperature performance thresholds.

API SQ, the corresponding API category, is already in market. SANYANG G3PLUS-6 and G3-6 carry formulation support for API SQ, ILSAC GF-7, ACEA 2023 and GM dexos1 Gen. 3.

The implication for lubricant blenders in Asia is direct. OEM-approved lubricant products sold into markets with BS VI (India), Guojia VI (China) or Euro VI equivalent standards will increasingly require Group III+ base stocks to meet both the performance specifications and the OEM approval requirements. Blenders still formulating on Group I or Group II for these applications face a forced transition within the current decade.

Section 7 — Procurement Guide: Choosing Between Group III and Group III+

For lubricant formulators and industrial buyers, the practical selection criteria are straightforward.

Use Group III (VI 120–129) when:

Formulating 5W-30, 5W-40, 10W-40 or 15W-40 products for markets where ILSAC GF-5, API SN or ACEA A3/B4 compliance is the target. Group III at VI 127 — such as SANYANG G3-6 — is cost-effective for these applications and delivers performance well above Group II equivalents.

Use Group III+ (VI ≥ 130) when:

Formulating 0W-16, 0W-20 or 0W-30 products targeting ILSAC GF-6, GF-7, API SQ, ACEA 2023 C5/C6, or GM dexos1 Gen. 3 compliance. The CCS viscosity at -35°C is the critical parameter — SANYANG G3PLUS-4 delivers 2,030 mPa.s at -35°C, well within the threshold for 0W-16 formulations.

Key PDS parameters to evaluate:

• KV100: kinematic viscosity at 100°C — determines the base viscosity grade
• Viscosity Index: higher VI means better performance across temperature range
• Noack Evaporation: lower is better — limits oil consumption at high temperature
• CCS @ -30°C and -35°C: cold crank simulator — determines low-temperature pumpability
• Sulphur content: ≤ 10 mg/kg for Group III+, ≤ 15 mg/kg for Group III
• Saturates: > 99% typical for quality Group III and Group III+ products

Always request COA per shipment batch. TDS values are indicative. Batch-specific Certificate of Analysis confirms actual tested properties for each cargo.

Related: see our guides on rubber process oil, white oil and bitumen for adjacent industrial petroleum portfolios supplied from Malaysia.

SANYANG G3 Series: Available Grades

Sanyang Petroleum supplies three Group III and Group III+ grades from Malaysia:

All three grades are NSF H1/HX-1 registered for incidental food contact applications. Full Product Data Sheets are available for download below or on the Group III base oil product page.

Download Product Data Sheets

Frequently Asked Questions