Medium TBN Calcium Sulfonate is the workhorse detergent for standard passenger car motor oils (0W-20 through 15W-40) and light-to-medium diesel engine oils not subject to ACEA C-sequence low-SAPS restrictions. It provides the full TBN contribution, high-temperature detergency, and corrosion protection required by API SP/SN, ACEA A3/B4, and similar specifications at economically optimal treat rates - balancing TBN delivery, sulphated ash, and cost per formulated litre.

This is the primary application differentiating Medium TBN from Low TBN calcium sulfonate. Calcium sulfonate grease is produced by converting the colloidal CaCO₃ micelles in Medium TBN (or High TBN) calcium sulfonate into a crystalline calcite network thickener structure, using a promoter (typically 12-hydroxystearic acid or boric acid) and a controlled thermal conversion process. The resulting grease thickener is amorphous at first, then crystallises to a calcite structure on cooling - providing the grease with exceptional mechanical stability and high dropping point (>300°C).

Medium-speed marine trunk piston engines (TPEO, TBN typically 20–40 mgKOH/g in finished oil), gas engines, and stationary diesel generators operating on distillate or natural gas fuels require moderate TBN detergent additives. Medium TBN Calcium Sulfonate provides the acid neutralisation reserve needed for moderate fuel sulphur content and the rust inhibition required in marine environments (seawater exposure, humidity) without the extreme TBN levels of crosshead marine TPEO grades.

In heavy-duty industrial gear oils, compressor oils, and turbine/circulating oils subject to moderate acid loads and extended service periods, Medium TBN Ca sulfonate provides detergency, rust inhibition, and acid-scavenging performance in a single component. At lower treat rates (0.5–2.0 wt%), it supplements the primary antioxidant and rust inhibitor packages with alkalinity reserve - extending the service life of the lubricant by retarding acid-induced degradation and metal corrosion.

Q: What TBN sub-grade of Medium TBN Calcium Sulfonate is best for calcium sulfonate grease production?

The most widely used sub-grades for calcium sulfonate grease manufacturing are TBN 150–250 mgKOH/g. Higher TBN within the Medium range (250–300) provides a higher colloidal CaCO₃ content per kilogram, which translates to a higher thickener yield per unit weight of base material - meaning less raw material is required to reach the target NLGI grade. However, higher TBN sub-grades are also more viscous and more costly. The optimal sub-grade depends on your grease formulation target (NLGI grade, base oil ratio, complex agent content) and process parameters. Sinolook's technical team can recommend the appropriate sub-grade for your specific grease production process.

Q: What is the difference between Medium TBN and High TBN Calcium Sulfonate for engine oil formulation?

The key trade-off is TBN delivery vs sulphated ash contribution. High TBN (300–400 mgKOH/g) delivers more acid-neutralisation reserve per kilogram of additive - essential for heavy-duty diesel on sulphur-containing fuel, long-drain commercial vehicle oils (API CK-4, ACEA E6/E9), and other applications where TBN must remain above a minimum threshold throughout an extended drain interval. Medium TBN is the preferred choice where a moderate TBN contribution is required without the high sulphated ash of High TBN concentrate - particularly for standard PCMO and light commercial vehicle oils where total finished oil sulphated ash of 1.0–1.5 wt% is the target range. Many formulations blend Medium and High TBN to achieve cost-optimised TBN delivery.

Q: Can Medium TBN Calcium Sulfonate be used in ACEA C-sequence (low-SAPS) engine oils?

Generally not as the primary detergent at standard treat rates. ACEA C1/C2/C3/C5 limit sulphated ash to 0.5–1.0 wt% in the finished oil. At the Ca content of Medium TBN grade (3–10 wt% Ca), even a modest 2 wt% treat rate would contribute 0.20–0.68 wt% sulphated ash - significantly limiting the ash headroom available for ZDDP and potentially exceeding C1/C2 limits. Low TBN Calcium Sulfonate is the specified grade for ACEA C-sequence formulation. However, very small blending proportions of Medium TBN Ca sulfonate (<1 wt%) can be used in C-sequence formulations if the ash balance permits, to supplement the TBN contribution of the Low TBN base detergent.

Q: Why does Medium TBN Calcium Sulfonate have higher viscosity and density than Low TBN?

Both viscosity and density increase with TBN because higher TBN requires more colloidal CaCO₃ micelles per unit volume of product. CaCO₃ (density ~2.7 g/cm³) is significantly denser than base oil (~0.86 g/cm³), raising the overall product density to 0.95–1.05 g/cm³ at Medium TBN vs ~0.90–0.96 g/cm³ for Low TBN. The colloidal micelles also increase the product's intrinsic viscosity. In practice, this means Medium TBN Ca sulfonate may require warming to 40–50°C for effective pumping and blending in cold weather - and density must be accounted for when converting treat rates from wt% to vol% in blending calculations.

Related: Low TBN Calcium Sulfonate · High TBN Calcium Sulfonate · Overbased Calcium Sulfonate · Overbased Magnesium Sulfonate · Primary ZDDP · PIB Succinimide Dispersant