API ILSAC ACEA Gasoline and Diesel Engine Oil Standards and Specifications
API, ILSAC, and ACEA Engine Oil Specifications
This article provides an in-depth technical overview of the major engine oil specification systems used worldwide: API Service Categories for gasoline and diesel engines in North America, the ILSAC standards for fuel economy and emissions-friendly gasoline oils, and the ACEA performance classes defined by European manufacturers. Each section contains detailed descriptions of test protocols, performance targets, and the rationale behind each category's introduction.
1. API Service Categories
1.1 Gasoline Engines (“S‑Series”)
The API “S‑series” designations date back to the mid‑1960s and have evolved to address increasingly stringent requirements for oxidation control, high‐temperature deposit protection, cold‐start performance, and compatibility with modern emissions and fuel‐economy demands. Each category builds on its predecessor, retaining all prior performance tests (sludge control, wear, volatility) while adding new test sequences to simulate real‐world engine stresses.
| Category | Years | Technical Highlights |
|---|---|---|
| SA | Pre‑1930 | Viscosity grade only; no additive requirements. Suitable for flat‐head and early overhead‐valve engines. |
| SB | 1930–1963 | Introduced basic oxidation inhibitors (amine‐ and phenolic‐based) to resist oil thickening and varnish. |
| SC | 1964–1967 | Added corrosion inhibitors (phosphate esters) and improved dispersants to handle early deposit and acid‐byproduct control. |
| SD | 1968–1971 | Enhanced thermal and oxidative stability tests (ASTM D943) to protect at sustained 150 °C under scavenging conditions. |
| SE | 1972–1979 | Incorporated sequence VE (sludge test) and sequence VID (detergent/dispersant) for heavy‐duty and turbocharged engines. |
| SF | 1980–1988 | Improved volatility (NOACK ≤ 15 %) and high‐temp high‐shear (HTHS ≥ 2.9 cP at 150 °C) requirements for tighter tolerance engines. |
| SG | 1989–1993 | Added piston cleanliness test (sequence IIIG) and more severe sludge/vandish (sequence IIID) for extended drain intervals. |
| SH | 1993–1996 | Introduced HTHS viscosity ≥ 2.9 cP and tightened volatility to NOACK ≤ 12 % to protect catalytic converters and oxygen sensors. |
| SJ | 1996–2001 | Tightened evaporation loss (Sequence VIE), improved low‐temperature cranking viscosity (CCS ≤ 3,500 mPa·s at −25 °C). |
| SL | 2001–2004 | Enhanced deposit control via modified sequence IIIG and IIIF tests; introduced piston varnish limits. |
| SM | 2004–2010 | Added LSPI mitigation requirements (sequence VG fuel‐economy test) and extended oxidation resistance targets. |
| SN | 2010–2020 | Included turbocharger protection (sequence IVC), more stringent catalyst compatibility (SO₂ generation limits), and resource‐conserving options (ILSAC GF‑5 alignment). |
| SP | 2020–2025 | Mandatory LSPI control (sequence IX), timing‐chain wear tests (OECS‑B1 bench), E85 compatibility, and enhanced high‐temp deposit control (sequence IIIG updated). |
| SN Plus | 2018–present | Supplement to SN adding Sequence IX LSPI test on Ford 2.0 L EcoBoost engine: ≤ 5 events per test run to validate LSPI suppression. |
| SQ | 2025–present | Builds on SP with:
|
1.2 Diesel Engines (“C/F‑Series”)
Heavy‐duty diesel oils face extreme soot loading, high base-acid neutralization demands, and after‐treatment compatibility (DPF, SCR). The API C‑series evolved from simple TBN/wear tests to complex HTHS and DPF protection protocols.
| Category | Year | Performance Criteria |
|---|---|---|
| CA | 1949 | Base TBN ≥ 6 mg KOH/g; wear control (D7625 engine test). |
| CB | 1961 | Improved deposit control (sludge sequence VE); TBN ≥ 7 mg KOH/g. |
| CC | 1961 | Detergent/dispersant engine test (sequence VID); soot handling. |
| CD | 1955 | High‑speed four‐stroke engine test (sequence IIAA); TBN ≥ 10 mg KOH/g. |
| CE | 1985 | Extended drain 500 h test; improved oxidation stability (PDSC & TOST). |
| CF‑4 | 1990 | Turbo & DI compatibility (sequence IID); high‐temp deposit control. |
| CG‑4 | 1995 | Severe‑duty JASO DH‐2 soot & wear tests; improved TBN retention. |
| CH‑4 | 1998 | 1998 EPA exhaust standards; HTHS ≥ 3.5 cP; low‐temp pumpability (CCS). |
| CI‑4 | 2002 | EGR soot control (sequence IIIF variant); elastomer compatibility tests. |
| CI‑4 PLUS | 2004 | Shear stability test (sequence IVA); enhanced soot viscosity control. |
| CJ‑4 | 2006 | DPF protect: sulfated ash ≤ 0.30 %; phosphorus ≤ 0.08 %; sulfur ≤ 0.30 %. |
| CK‑4 | 2017 | Backward‐compatible; new aeration (sequence VD), oxidation (TOST), and viscosity loss tests. |
| FA‑4 | 2017 | Fuel economy XW‑30 oils; HTHS 2.9–3.5 cP; low‐sulfur fuel only. |
2. ILSAC Specifications
ILSAC standards, co‐branded with API, focus on passenger car gasoline oils that deliver improved fuel economy, emission system protection, and performance targets aligned with automaker requirements.
| Standard | Year | Test Requirements |
|---|---|---|
| GF‑1 | 1993 | Early fuel economy bench tests (CEC L‑36‐A); moderate HTHS & volatility controls. |
| GF‑2 | 1996 | Improved LSPI bench evaluation; lower volatility (NOACK ≤ 15 %) and tighter HTHS. |
| GF‑3 | 2001 | Sequence IIIG/IIIF deposit & wear tests; emission system compatibility (OECS‑A1 bench). |
| GF‑4 | 2004 | Introduced Sequence IX (LSPI) and GM dexos requirements. |
| GF‑5 | 2010 | Low SAPS (sulfated ash ≤ 0.8 %), improved LSPI, ILSAC resource conserving labels. |
| GF‑6A | 2017 | 0W‑16 grade support; volatile limits tightened; LSPI and timing‐chain tests. |
| GF‑6B | 2017 | Exclusively for 0W‑8 & 0W‑12; severe low‐temp fluidity tests. |
| GF‑7A (Starburst) | 2025 | Aligns fully with API SQ: ultra‐low viscosities, LSPI, deposit control, GPF‐safe ash ≤ 0.9 %. |
| GF‑7B (Shield) | 2025 | For SAE 0W‑16/0W‑8/0W‑12 only; Starburst plus enhanced low‐temp and deposit tests. |
3. ACEA Specifications
3.1 Passenger Car Oils (Gasoline & Diesel)
ACEA standards emphasize extended drain, emission‐control compatibility (DPF, CAT), and fuel economy. They are split into A/B (gasoline+dsl) and C (low SAPS for after‐treatment).
| Category | Application | Key Criteria |
|---|---|---|
| A1/B1 | Gas & DSL | HTHS 2.6–2.9 cP; Sequence X (fuel economy); limited TBN |
| A3/B3 | High‐perf Gas & DSL | HTHS ≥ 3.5 cP; Sequence B engine tests; extended drain |
| A3/B4 | Gasoline & DSL | A3 plus DSL soot handling sequence M111; DPF compatibility |
| A5/B5 | Gas & DSL | HTHS 2.6–3.0 cP; fuel economy; extended drain |
| C1 | Low SAPS Gas & DSL | DPF protect; HTHS 2.6–2.9 cP; Sequence B4 |
| C2 | Low SAPS Gas & DSL | DPF; HTHS 2.9–3.5 cP; Sequence C tests |
| C3 | Mid SAPS Gas & DSL | DPF; HTHS ≥ 3.5 cP; Sequence C performance |
| C4 | Low SAPS DSL | DPF; extended drain 100,000 km |
3.2 Heavy-Duty Diesel Oils
ACEA E‐categories cover commercial diesel applications from long-haul to off‐road, with stringent tests for soot, oxidation, and after‐treatment protection.
| Category | Application | Key Requirements |
|---|---|---|
| E4 | Heavy‐duty | Sequence X; high HTHS & TBN; extended drain |
| E6 | Low SAPS | DPF protect; extended drain; oxidation & corrosion tests |
| E7 | High perf Diesel | High soot & HTHS; Sequence OM645 test |
| E9 | Mid SAPS | DPF; OM646 engine test; high HTHS |
4. Conclusion
The landscape of engine oil specifications spans multiple standards tailored to engine type, emissions control, and performance goals. API, ILSAC, and ACEA each provide complementary frameworks to ensure oils meet the demands of modern powerplants, from passenger cars to heavy‐duty trucks. Always reference the latest Donut, Starburst/Shield, or ACEA badge when selecting engine oil for optimal protection and compliance.