Base oils & additives
A group is three numbers, guaranteed together. Anything less is a heading.
Lubricant base stocks across the API groups, plus naphthenic grades, white oils, process oils and the additive chemistry that goes with them — every parcel offered against a batch Certificate of Analysis, not a typicals sheet.
The desk
The most mis-sold product in the refined barrel.
Base oil is bought on a group designation, and the group designation is the thing most often wrong on the paperwork. API 1509 defines a group on three parameters — saturates, sulphur and viscosity index — and all three must be satisfied simultaneously. A sheet that reports viscosity index and omits saturates has not established anything.
This matters commercially, not just technically. A Group II sold as Group III carries a real price difference per tonne, and the blender who buys it discovers the problem when the finished oil fails a Noack or a cold-crank test months later, with the cargo long since consumed and the claim window closed.
So we test the claim before the offer goes out. Where a supplier's datasheet cannot establish the group it is headed with, we say so and re-paper the offer to the grade the parcel actually is. That occasionally loses us a trade. It has never lost us a blender.
API 1509
What the groups actually mean.
Five groups, defined by composition and viscosity index rather than by marketing category. Groups I to III are mineral stocks separated by how severely they have been processed; IV and V are synthetics.
| Group | Saturates | Sulphur | Viscosity index | Production route | Typical use |
|---|---|---|---|---|---|
| Group I | < 90 % | > 0.03 % | 80–120 | Solvent refining | Monograde, marine, industrial, greases |
| Group II | ≥ 90 % | ≤ 0.03 % | 80–120 | Hydrotreating / hydrocracking | Mainstream PCMO and HDEO formulation |
| Group III | ≥ 90 % | ≤ 0.03 % | > 120 | Severe hydrocracking, catalytic dewaxing | Low-viscosity synthetic-claim engine oils |
| Group IV | Polyalphaolefin (PAO) | > 120 | Chemical synthesis | Full synthetics, extreme temperature range | |
| Group V | Everything else — esters, PAG, alkylnaphthalene, naphthenic, white oils | — | Various | Co-base stocks, specialities, process oils | |
The slate
What we supply.
Group I — solvent refined
The original base stock and still the workhorse of GCC, African, South Asian and Turkish blending. Solvent refining leaves aromatics and sulphur in the oil, which is precisely why Group I remains preferred where solvency and additive response matter more than volatility — greases, marine cylinder oils, metalworking fluids, process applications and monograde engine oils.
The SN designation means solvent neutral, and the number is the cut's approximate Saybolt Universal Seconds viscosity — which is why the series runs 150, 180, 300, 350, 500, 600, 650 rather than in round steps. The ranges below are indicative: the exact limits are producer-specific, so the grade on the offer is only as good as the batch certificate behind it.
Global Group I capacity has been closing for a decade as refiners convert to Group II, which has made Bright Stock in particular structurally tight. There is no Group II or III equivalent to Bright Stock, so formulations that need it need it.
- SN 150
- 5.0–5.7 cSt at 100 °C, viscosity index 89 minimum, flash point 200 °C minimum. Light hydraulic, textile and transmission fluids, and where fast circulation or cold flow matters.
- SN 180
- Around 5.7 cSt at 100 °C and 35 cSt at 40 °C, viscosity index typically near 100, flash point around 230 °C. A light-medium cut for engine and transmission oils, greases and hydraulics — a useful step up from SN 150 without moving to a 300.
- SN 300
- 6.5–8.0 cSt at 100 °C, viscosity index 89 minimum, flash point 210 °C minimum. General industrial and automotive blending; the common mid cut where SN 150 is too light and SN 500 too heavy.
- SN 350
- The adjacent mid cut to SN 300, produced by some refiners in place of it. Interchangeable in most formulations, but confirm which one the offer is against — the viscosity bands overlap and the labels do not.
- SN 500
- 10.3–11.7 cSt at 100 °C, viscosity index 89 minimum, flash point 230 °C minimum. The volume grade — heavy-duty engine, gear and marine lubricants where film strength under load and temperature is the requirement.
- SN 600
- 11.6–13.5 cSt at 100 °C, viscosity index 90 minimum, flash point 240 °C minimum, pour point −6 °C maximum. Heavier engine and gear formulations, and a common Bright Stock extender where a full residual cut is not needed.
- SN 650 and heavier
- The top of the neutral range, into gear oils, greases and industrial formulations. SN 900 (19.0–22.0 cSt at 100 °C, flash point 260 °C minimum) available from some producers where a heavy neutral is preferred to Bright Stock.
- Bright Stock (BS 150)
- Residual, deasphalted and dewaxed. 29.0–34.0 cSt at 100 °C, flash point 280 °C minimum. High viscosity and tackiness for marine cylinder oils, gear oils, greases and heavy industrial applications. No lighter-group substitute exists.
Group II — hydrotreated
The current mainstream feedstock for passenger-car and heavy-duty engine oils. Hydroprocessing removes sulphur and aromatics and saturates the oil, giving better oxidation stability, cleaner colour and lower volatility than Group I at comparable viscosity.
The trade-off is solvency: Group II dissolves additives and holds degradation products less readily than Group I, which is a formulation question rather than a quality one. Blenders switching from Group I generally re-check seal compatibility and additive solubility rather than assuming a drop-in.
- Grades
- N 100, N 150, N 220, N 500, N 600 and adjacent cuts, plus Group II bright stock equivalents where produced.
- Defining parameters
- Saturates at 90 % or above, sulphur at or below 0.03 %, viscosity index 80–120 — all three reported, or the group is not established.
- Applications
- API SP and ILSAC GF-6 passenger-car oils, CK-4 and FA-4 heavy-duty diesel oils, hydraulic and turbine oils, ATF, and food-grade adjacent formulations.
- Why blenders move to it
- Longer drain intervals, better thermal and oxidative stability, and easier compliance with volatility limits in current engine-oil specifications.
Group III — severely hydrocracked
Viscosity index above 120, achieved by severe hydrocracking followed by catalytic dewaxing. This is the base of most oils sold as synthetic outside the PAO segment, and the enabling stock for the low-viscosity grades — 0W-20, 0W-16 — that current fuel-economy standards push formulators toward.
Catalytic dewaxing is the tell. Genuine Group III pours at −12 °C or below and holds a tight Noack; a solvent-dewaxed stock dressed up with a viscosity index improver does neither. Pour point and Noack volatility are the two parameters we insist on seeing on the batch CoA, because they are the two a look-alike cannot fake.
- 4 cSt
- 4.0–4.5 cSt at 100 °C, viscosity index 120 minimum, pour point −12 °C maximum, flash point 200 °C minimum, Noack typically below 18 %. The workhorse of 0W and 5W formulations.
- 6 cSt
- 5.6–6.2 cSt at 100 °C, flash point 220 °C minimum, Noack typically below 8 %.
- 8 cSt
- 7.6–8.2 cSt at 100 °C, flash point 240 °C minimum, Noack typically below 7 %. Heavier synthetic-claim formulations and gear oils.
- Group III+ and GTL
- Viscosity index in the 130s and above, from gas-to-liquid or highly severe conventional routes, where the formulation is reaching toward PAO performance without PAO cost. Available subject to origin and allocation.
Re-refined base oils
Used lubricating oil collected, dehydrated, vacuum distilled and hydrotreated back to a virgin-equivalent stock. Modern re-refineries produce material that meets Group II specifications on saturates, sulphur and viscosity index — the same three parameters, tested the same way, from a circular feedstock.
The commercial case is that it is a specification-equivalent stock with a materially lower carbon footprint, not that it is cheap. The technical case is that it should be bought on exactly the same CoA discipline as virgin material, which is how we offer it.
- Grades
- Group I+ and Group II equivalents across the common neutral cuts, from certified re-refiners.
- Evidence supplied
- Batch CoA against the same parameter set as virgin stock, plus the re-refiner's certification and, where the buyer's reporting requires it, recycled-content documentation.
- Where it fits
- Industrial, hydraulic and general automotive formulations, and any programme with a recycled-content or carbon-reduction target — see Sustainability.
- What we will not claim
- That re-refined stock is a drop-in for every formulation. Additive response is checked on the parcel, like any other base oil.
Naphthenic and process oils
Naphthenic stocks — Group V by API classification — are low in wax and high in solvency, which gives them naturally low pour points without dewaxing and makes them the base of choice for transformer oils, refrigeration oils, metalworking fluids, printing inks, adhesives and rubber compounding.
Rubber process oils carry a regulatory constraint most buyers underestimate. In the EU, extender oils in tyres must contain less than 1 mg/kg benzo[a]pyrene and less than 10 mg/kg total of the eight listed polycyclic aromatic hydrocarbons, tested to EN 16143 — a restriction in force since 1 January 2010 which removed conventional DAE from the European tyre market.
- Naphthenic base oils
- Pale oil cuts across the light-to-heavy viscosity range for transformer, refrigeration, metalworking and speciality formulation.
- Transformer oil
- Inhibited and uninhibited grades against IEC 60296 and equivalent national specifications.
- Rubber process oils
- TDAE — the closest performance match to DAE and the dominant tyre-tread replacement — plus MES, RAE, naphthenic and paraffinic process grades.
- Compliance note
- Where a destination applies the PAH restriction, we quote a compliant grade and supply the EN 16143 result. We will not offer a non-compliant extender oil into a market that restricts it.
White oils — technical and pharmaceutical
Highly refined, colourless, odourless mineral oils. The controlling tests here are not the API group parameters — purity is what is being bought, evidenced by ultraviolet absorbance, readily carbonizable substances and the absence of aromatics, against the pharmacopoeia or food-contact regulation that governs the end use.
Grade selection follows the regulation, not the viscosity. A cosmetic formulator, a food-processing plant lubricating a conveyor and a pharmaceutical manufacturer are working to three different documents, and a certificate against the wrong one is worth nothing at audit.
- Pharmaceutical / medicinal grade
- Against USP and Ph. Eur. monographs — identification, UV absorbance, readily carbonizable substances, heavy metals and microbial limits.
- Food-contact grades
- FDA 21 CFR 172.878 for direct food additive use, and 21 CFR 178.3620 for incidental contact including food-machinery lubricants.
- Technical white oils
- Textile, plastics, polystyrene, agricultural spray oil and general industrial grades where pharmacopoeial purity is not required.
- Documentation
- Batch CoA against the named monograph or CFR section, plus SDS under REACH / CLP or GHS in the destination language.
Additive packages and components
Base oil is 70–90 % of a finished lubricant by volume and rarely the reason it passes or fails a specification. The additive package does that work — detergents, dispersants, anti-wear, antioxidants, friction modifiers, corrosion inhibitors, anti-foam — and it is engineered against the performance claim, not against the base stock.
Current engine-oil claims are demanding in specific ways. API SP and ILSAC GF-6, in force since 2020, added the Sequence IX low-speed pre-ignition test and the Sequence X timing-chain wear test, neither of which existed under SN Plus. A package that predates them does not meet them, whatever the drum says.
- DI packages
- Detergent-inhibitor packages for passenger-car (API SP / ILSAC GF-6A and GF-6B), heavy-duty diesel (API CK-4, FA-4) and ACEA sequence claims.
- Viscosity modifiers
- Polymeric VII for multigrade formulation, selected on shear stability index as well as thickening efficiency.
- Pour point depressants
- Matched to the base stock — a PPD optimised for a solvent-dewaxed Group I will not perform the same on a catalytically dewaxed Group III.
- Speciality components
- Gear, hydraulic, grease, metalworking and industrial packages, plus heavy alkylbenzene for lubricant, grease and transformer-oil formulation — traded on the chemicals desk, see Detergent alkylates & normal paraffins.
How to specify
Six lines get you a firm offer.
"SN 500, 2,000 tonnes" is a starting point, not an enquiry. These six lines let a trader come back with availability, a level and the right parcel format first time.
Grade and group
The cut and the API group you need it to satisfy — and say if the group is a hard requirement rather than a description, because that changes which parcels qualify.
The parameters that must be guaranteed
Viscosity index minimum, pour point maximum, Noack and CCS if the formulation depends on them. Anything you list as guaranteed, we guarantee or decline.
What you are formulating
The finished-product claim — API SP, CK-4, an ACEA sequence, a transformer oil to IEC 60296, a USP white oil. It determines which parcels are even candidates.
Quantity, delivery basis and format
Tonnes, FOB / CIF / CFR or delivered, and whether the plant takes flexitank, ISO tank, drums or bulk.
Receiving facility
Tank capacity, heating, and whether the tank is dedicated or in shared service — cross-contamination risk changes what we are willing to load into it.
Timing and documentation
Laycan or delivery window, and any pharmacopoeial, food-contact, halal or destination-specific certification the cargo must carry.
Quality
How we vet a grade.
Every parcel is offered against a batch Certificate of Analysis from the producing refinery or an independent laboratory. Inspection, where appointed, is by SGS, Bureau Veritas or Intertek — not by the supplier and not by us.
Base oil is unusually easy to misrepresent and unusually hard to correct after the fact. It arrives clear, it smells like base oil, and the defect only surfaces when the blend fails a bench test weeks later. The defence is a batch certificate against the full parameter set, on the parcel you are buying, from a laboratory with no position in the trade.
- The parameter set
- Viscosity index by D2270 as a guaranteed minimum; kinematic viscosity at 40 and 100 °C by D445; pour point as a maximum by D97; flash point by D92; density at 15 °C by D4052; sulphur by D2622 or D4294; saturates by D2007; colour by D1500.
- Where the application demands it
- Noack volatility by D5800 and cold-cranking simulator by D5293 for engine-oil stocks; UV absorbance and readily carbonizable substances for white oils; EN 16143 PAH for extender oils; dielectric and oxidation stability for transformer grades.
- Group verification
- Saturates, sulphur and viscosity index reported together. Where a datasheet omits one, the group is unestablished and we say so before quoting rather than after loading.
- Per consignment
- Certificate of Analysis, Certificate of Origin, SDS under REACH / CLP or GHS in the destination language, packing list, and independent inspection report where appointed.
Packaging and delivery
Cleanliness is part of the specification.
Base oil picks up whatever was in the tank before it. Prior-cargo history and dedicated service matter as much as the packing format, and both are agreed before a parcel is fixed.
| Format | Typical capacity | Suited to | Notes |
|---|---|---|---|
| Bulk tanker | Vessel and road tanker parcels | Blending plants with dedicated tankage | Prior-cargo history and tank-cleaning certificate agreed in advance |
| ISO tank container | ~20–26 m³ | Mid-size parcels, speciality and white oils | Dedicated or cleaned to a stated standard; heating where required |
| Flexitank | ~18,000–24,000 L in a 20-ft container | Cost-efficient single-use parcels on liner routes | Single-use liner removes prior-cargo risk entirely |
| New steel drums | ~208 L / 180 kg | Distribution, smaller blenders, speciality grades | New drums for white and pharmaceutical grades as standard |
| IBC | 1,000 L | Additive packages, speciality and sample quantities | Preferred format for additive chemistry |
Straight answer
What we will tell you before you ask.
- Where the group claim is not established
- If saturates, sulphur and viscosity index are not all on the certificate, the group on the heading is an assertion. We re-paper the offer to the grade the parcel actually is, and price it accordingly.
- Where a substitution is a reformulation
- Group III for Group IV, Group II for Group I, re-refined for virgin — each can be right, and none is automatic. We will flag where a swap needs bench work rather than letting it arrive as a surprise.
- Where a regulation governs the grade
- PAH limits on extender oils, pharmacopoeial monographs on white oils, food-contact CFR sections — raised at enquiry, with the test result supplied, not discovered at customs.
- Where we cannot clear the origin
- Origin is screened per consignment before we quote. Where it cannot be cleared we decline rather than structure around it — see Compliance.
Enquiries
Every enquiry is answered by the desk that handles it.
Send the product, quantity, delivery basis, destination and timing. We revert with availability, an indication and the documentation that accompanies it. Specifications are released once we know who we are speaking with.