Overbased calcium sulfonate detergent is a high-alkalinity lubricant additive that neutralises acids, cleans engine surfaces and protects against corrosion. It is the backbone of modern engine oil cleanliness and a core component of diesel and marine formulations. This guide explains its chemistry, TBN levels and how to select the right grade.
What Is an Overbased Calcium Sulfonate Detergent?
An overbased calcium sulfonate is produced by reacting long-chain alkyl benzene sulfonic acid with lime and carbon dioxide to create a colloidal calcium carbonate core stabilised by calcium sulfonate. The result is a reserve of alkalinity suspended in oil: when combustion acids form, the carbonate core neutralises them before they can attack metal surfaces. Key grades produced by Shanghai Minglan Chemical:
| Grade | TBN (mgKOH/g) | Calcium (m%) | Typical use |
|---|---|---|---|
| T104 (synthetic, low base) | ≥ 170 | ≥ 2.0 | Marine and industrial oils, rust inhibition |
| T106 (synthetic, high base) | ≥ 295 | ≥ 11.5 | Diesel engine oils, heavy-duty formulations |
| T106D (super overbased) | ≥ 395 | ≥ 14.5 | High-TBN diesel and marine cylinder oils |
All grades are red-brown viscous liquids tested per ASTM D2896 (TBN), ASTM D5185 (metals) and ASTM D445 (viscosity). See the detergent product range for full specifications.
Why TBN Matters
TBN (total base number) measures the detergent’s acid-neutralising capacity. Diesel combustion produces sulfuric acid from fuel sulfur; if the oil cannot neutralise it, corrosive wear follows. Matching TBN to fuel sulfur and drain interval is the core of detergent selection:
- Low-sulfur diesel (CF-4/CH-4): TBN 20-40 packages using T104/T106 blends.
- High-sulfur diesel (CI-4, CK-4): TBN 40-60 packages, typically built on T106/T106D.
- Marine cylinder oils: TBN 40-100, built on super-overbased sulfonates such as T106D.
Selection Guide
- Start from the target oil performance level and its TBN requirement.
- Choose the sulfonate grade whose TBN contribution fits the treat rate window (usually 1-3% in the package).
- Verify compatibility with your dispersant, ZDDP and antioxidant in a bench test – sulfonate grades differ in compatibility.
- Confirm water, mechanical impurities and low-temperature behaviour meet your QC limits.
Source From a Specialist Manufacturer
Shanghai Minglan Chemical manufactures the full detergent family – synthetic calcium sulfonates (T104/T106/T106D), calcium salicylates, phenates and magnesium sulfonates – with in-house TBN and metals testing on every batch. Contact info@lubeadditive.com for specifications, samples and pricing.
