Overbased calcium sulfonate is the most-used detergent chemistry in modern PCMO and HDD engine oil — it neutralises acidic combustion products, suspends sludge precursors and provides reserve alkalinity (TBN). This guide covers synthetic alkylbenzene sulphonic acid (SABS) feedstock, the CO2 carbonation manufacturing process, TBN selection (300 / 400 / 500) by service category, branded suppliers (Lubrizol / Afton / Infineum / Chevron Oronite / IPAC), and the custom Indian-blended route at 35-42% cost saving with formula IP transferred to the client.
| Service Category | Detergent Type | Treat % in Finished | Finished Oil TBN |
|---|---|---|---|
| PCMO API SP / GF-6 | Ca + Mg sulfonate TBN 400 + salicylate | 2-3% | 7-9 |
| PCMO API SN | Ca sulfonate TBN 300-400 | 2-3% | 6-8 |
| HDD API CK-4 | Ca sulfonate TBN 400-500 | 3-4% | 10-13 |
| HDD API FA-4 low-VG | Ca + Mg sulfonate TBN 300 (Mg-rich) | 2-3% | 7-9 |
| Marine System Oil | Ca salicylate TBN 300 | 3-5% | 9-12 |
| Marine Cylinder 100 TBN | Ca sulfonate TBN 500 + phenate booster | 15-25% | 70-100 |
| Gear Oil GL-5 / Industrial | Ca sulfonate TBN 300 (CI role) | 0.5-1.5% | 2-4 |
| Property | Test Method | TBN 300 Target | TBN 400 Target | TBN 500 Target |
|---|---|---|---|---|
| Total Base Number (TBN) | ASTM D2896 | 295-310 | 395-410 | 495-510 |
| Calcium content (% m/m) | ICP-OES | 8.5-9.5 | 11.2-12.0 | 13.5-14.5 |
| Viscosity @ 100 °C (cSt) | ASTM D445 | 28-40 | 100-160 | 600-900 |
| Solubility in base oil | Visual at 20:80 dilution | Clear, no haze | Clear, no haze | Clear, no haze |
| Reserve alkalinity | D5984 | Pass | Pass | Pass |
| Filterability | In-house (5 µm, <30 sec) | Pass | Pass | Pass |
| Foam at 50 °C | ASTM D892 Seq I | <25 ml | <25 ml | <30 ml |
| Storage stability 7-day 60 °C | In-house visual | No haze, no sediment | No haze, no sediment | Slight haze acceptable |
Match overbased Ca sulfonate TBN to the service: PCMO API SP needs finished TBN 7-9, use TBN 300-400 detergent at 2-3% treat; HDD CK-4 needs finished TBN 10-13, use TBN 400-500 at 3-4% treat; marine system oil needs finished TBN 9-12, use TBN 300 salicylate at 3-5% treat; marine cylinder oil needs finished TBN 70-100, use TBN 500 sulfonate + booster at 15-25% treat.
Industrial R&O turbine uses no detergent (residual TBN <2); gear oil uses small TBN 300 for CI role at 0.5-1.5%.
Neutral Ca sulfonate (TBN 20-50) is the direct stoichiometric salt of sulphonic acid and lime — only modest base reserve. Overbased Ca sulfonate (TBN 300-500) carries 6-10× more calcium per molecule as colloidal CaCO3 micelle stabilised by the sulfonate surfactant.
Overbasing is achieved by adding excess lime + methanol promoter and sparging CO2 to convert Ca(OH)2 to CaCO3 inside the micelle. Overbased gives the high reserve alkalinity needed for engine and marine — neutral is largely a corrosion-inhibitor / co-emulsifier role today.
Three coupled reactions. (1) Sulphonic acid + Ca(OH)2 → Ca sulfonate (neutral) + H2O — primary salt-formation. (2) Excess Ca(OH)2 dispersed by methanol as fine particles inside the sulfonate micelle. (3) CO2 sparge: Ca(OH)2 + CO2 → CaCO3 + H2O — the colloidal CaCO3 stays trapped inside the micelle.
After dehydration and methanol stripping, the product is a stable single-phase overbased detergent with TBN 300-500 depending on the Ca:sulfonate stoichiometry. Methanol is recovered and recycled.
SABS = Synthetic Alkylbenzene Sulphonic Acid, made by sulphonating C20-C32 linear or branched alkylbenzene with SO3 (oleum or gas). The alkyl chain length controls oil solubility — shorter chain (C16-C20) gives high water solubility (cleaning detergents); longer chain (C20-C32) gives oil solubility (lubricant detergents).
Indian SABS feedstock from BRB International (Belgium with Indian distribution), IPAC India (Mumbai), Stepan (US import) and select Indian sulfonation houses in Mumbai / Gujarat.
Marine cylinder oil for two-stroke crosshead diesel (MAN B&W, Wärtsilä) requires 70-100 TBN finished oil to neutralise the high sulfur content of marine residual fuel. Built from TBN 500 overbased Ca sulfonate at 15-25% treat plus calcium phenate booster + dispersant + AW + AO.
The high active TBN matter precipitates the sulphuric acid from combustion before it attacks the cast-iron cylinder liner. CIMAC TGL E-class cylinder oil tests measure neutralisation rate and TBN retention through 250 hr run.
Sulfonate has best Indian-market availability and lowest cost per TBN unit. Calcium phenate (overbased calcium alkylphenate) has higher thermal stability and contributes secondary antioxidant function — used in marine cylinder oil and high-temperature industrial.
Calcium salicylate (overbased calcium alkylsalicylate) is the low-SAPS detergent of choice for ACEA C-class — better Mg compatibility, lower sulfated ash per TBN unit. Modern PCMO API SP often uses a sulfonate + salicylate hybrid for balanced performance.
Branded overbased Ca sulfonate TBN 400 from Lubrizol / Oronite / Infineum lands in India at ₹320-450 / kg depending on volume. Indian-blended from Lubechem / IPAC custom equivalents land at ₹190-260 / kg — 35-42% saving.
The manufacturing process is well-established public-domain chemistry; the saving comes from Indian feedstock sourcing (BRB Belgium via Mumbai, IPAC India) and absence of brand premium.
Yes — Lubechem custom detergent is built to client's spec with target TBN (300 / 400 / 500), Ca content, filterability, base oil compatibility (Group I vs II vs III), and storage stability hold.
Engagement: 4-6 weeks from SABS receipt to finished detergent in drum. MOQ 100-500 kg for custom; lab-scale samples 1 kg available for evaluation. Formula IP transferred at closeout — client owns the BOM and process method.
Share your target TBN (300 / 400 / 500), Ca content target, service category and volume requirement. We respond within one business day with a process plan, BOM and indicative cost.