Passenger Car Motor Oil (PCMO) Packages

The Selection Principle: Match the Grade to the Engine — Not “Higher Is Better”

This is the part the thin supplier listings skip, and it is where the choice is actually made. The right gasoline grade is set by the engine’s combustion technology and its emission hardware, not by reaching for the newest letter on the shelf:

• Turbo GDI is the hard constraint — it needs LSPI protection. A turbocharged gasoline direct-injection engine can suffer low-speed pre-ignition (LSPI), an abnormal combustion event violent enough to crack pistons and rings. A current API SP package — with a re-balanced detergent system that addresses LSPI — is the normal choice; API SN PLUS (2018) also introduced LSPI protection, but a pre-SN PLUS SN or SM package should not be assumed suitable for a turbo-GDI engine, no matter how “premium” it looks.
• The catalytic converter caps the chemistry. Phosphorus from anti-wear ZDDP poisons the three-way catalyst, so for ILSAC / Resource Conserving gasoline oils phosphorus is typically held around 0.06–0.08 mass%, with a phosphorus-retention requirement (ASTM D8111) where applicable. You cannot simply load more ZDDP for wear protection — the gasoline emission system constrains the additive in the same way a diesel particulate filter constrains a heavy-duty oil.
• Viscosity is an OEM and fuel-economy decision. Modern OEMs specify ultra-low viscosity (0W-20, 0W-16) for fuel economy; the package must protect at thin oil films and carry the Resource Conserving fuel-economy credit. A legacy 15W-40 fill is a different formulation target from a 0W-20 fuel-economy oil.
• Match the ILSAC / market demand, then use backward compatibility. Some markets require the current ILSAC consumer mark (GF-7A/GF-7B) or ACEA A3/B4; confirm what the finished oil must carry. Because newer API categories are backward compatible, an SP package covers an SN/SM/SL requirement — but only spend on SP chemistry where the engine actually needs it.

So the decision order is: combustion technology (turbo GDI → LSPI) → catalyst/phosphorus limit → OEM & ILSAC spec → viscosity / fuel-economy grade → backward-compatible tier. The grade comparison and selection notes below put that into practice.

What a PCMO DI Package Does

A passenger-car gasoline package carries four jobs in one concentrate, blended into base oil to make the finished oil:

• Deposit & sludge control. Detergents and dispersants keep pistons, rings and the valve train clean and hold combustion by-products in suspension — the high-temperature deposit and low-temperature sludge duty that each API tier tightens.
• Anti-wear within the phosphorus budget. ZDDP builds a protective tribofilm on cams and followers, but is dosed to stay inside the catalyst-protecting phosphorus limit of modern ILSAC gasoline oils — wear protection and emission-system durability balanced, not maximised blindly.
• Oxidation control & fuel economy. Antioxidants extend oil life at modern high operating temperatures; friction modifiers and a Resource Conserving balance support fuel economy at low viscosity.
• LSPI mitigation & seal compatibility, at the SP tier. The SP package re-balances detergent chemistry (notably the calcium / magnesium / molybdenum balance) to help control low-speed pre-ignition in turbo GDI engines, and protects elastomer seals and the timing chain against wear.

The CheMost Range — Choose by API Tier

One DI technology family across the API service ladder; each grade is formulated to its tier, with the top tier carrying LSPI and timing-chain protection. Open a grade to request its data sheet.

LSPI — The Modern PCMO Challenge

Low-speed pre-ignition is the single issue that reshaped gasoline engine oil chemistry, and it is what separates a current SP package from an older SN/SM one. In a downsized turbocharged gasoline direct-injection (GDI) engine running at low RPM and high load, the air–fuel charge can ignite before the spark — an uncontrolled, high-pressure event that can fracture a piston or ring land in a single occurrence.

LSPI is strongly linked to oil chemistry: certain calcium-based detergents promote it, while magnesium-based detergents and a controlled molybdenum balance help suppress it. API SN PLUS (2018) first introduced LSPI testing — the ASTM D8291 Sequence IX engine test — which API SP and ILSAC GF-6 then retained as part of the current gasoline performance framework. A CheMost SP package therefore is not just “SN with a higher number”: its detergent system is re-balanced to help control LSPI in the finished oil. Validating and licensing the finished oil against Sequence IX is the blender’s responsibility. This is why a turbo-GDI engine should not be run on a pre-SN PLUS package, and why the LSPI requirement — not the SAE viscosity — is usually the deciding factor for a modern gasoline fill.

Specifications — All Grades data on request

The concentrate fingerprint for each grade — TBN, the detergent metals (Ca/Mg), ZDDP (Zn/P), any molybdenum friction modifier, dispersant nitrogen and boron, viscosity and flash — published per grade as test data is confirmed. Request the current data sheet for any grade.

Values are concentrate (package) properties measured to ASTM methods, not finished-oil properties. Published as confirmed — request the current TDS for any grade.

Performance Coverage & Treat Rate

These are formulation targets per grade at the appropriate treat rate in a suitable base oil — not API licenses. The API licence (through API’s Engine Oil Licensing and Certification System, EOLCS) and the ILSAC consumer marks — the Starburst (current ILSAC GF-7A) and the Shield (current ILSAC GF-7B, 0W-16 only) — are held and displayed by the finished-oil marketer who tests and licenses the finished oil, not by the additive package. CheMost’s SP family is formulated to align with these ILSAC performance targets; the finished oil is what is licensed and marked.

• Treat rate rises with the tier. Each grade is dosed to its targeted API category in a suitable base oil; the SP package carries the most chemistry. Confirm the treat rate from the grade’s data sheet.
• Read performance with the right tests. TBN by ASTM D2896, phosphorus by ASTM D4951 against the catalyst cap, and LSPI by ASTM D8291 (Sequence IX) — the package contributes to all three, but the finished oil is what is licensed.

The Gasoline API Grade Ladder — From SJ to SP

Each API S-series category builds on the previous one and is backward compatible, so a higher grade can serve a lower requirement (if your owner’s manual asks for API SN, an SP oil provides full protection):

• SJ (1996) / SL (2001) / SM (2004) — progressively tighter deposit, oxidation and wear control for the engines of their era.
• SN (2010) — stronger high-temperature deposit, sludge and seal-compatibility control; includes the SN Resource Conserving (RC) fuel-economy variant and the phosphorus cap for catalyst protection.
• SN PLUS (2018) — a transitional upgrade that added the first LSPI protection requirement for turbo GDI engines.
• SP (2020) — the current top category; integrates full LSPI protection, timing-chain wear performance and stronger high-temperature oxidation control.

Alongside the API category, a passenger-car oil usually also carries an ILSAC consumer mark. That mark has moved on: ILSAC GF-7A and GF-7B became the current specifications on 31 March 2025 (carrying the Starburst and Shield marks), while GF-6A/GF-6B are scheduled to become obsolete on 1 October 2026. A current SP-level package is formulated to align with the GF-7 performance targets; GF-6B and GF-7B apply only to SAE 0W-16.

Common Applications

• Legacy passenger cars (SJ/SL): fleet maintenance of older vehicles in cost-led markets, conventional mineral fills — API SJ / SL packages.
• Mainstream cars & light trucks (SN/SM): the workhorse modern fill for naturally-aspirated and most port-injected engines — PA3066N, the widely exported grade.
• Turbo GDI engines (SP): downsized turbocharged direct-injection engines needing LSPI protection — Ford EcoBoost, VW TSI, Toyota Dynamic Force and similar — API SP package.
• Fuel-economy & low-viscosity fills: 0W-20 and 0W-16 oils carrying the Resource Conserving / GF-7 performance balance — API SP package.
• Private label & export: PA3066N (SN/SM) for blenders marketing their own passenger-car brands; SP for premium and OEM-aligned lines.

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