| abstract |
The detergent inhibitor package has been found to influence the viscometric properties of SAE 5W lubricants that have less than 5 mass % of non-conventional basestock, use a basestock that has an average base stock neutral number not less than 105, a calibrated Noack volatility of not more than 22 wt. % loss, and a kinematic viscosity at 100 DEG C. (kV 100, measured by ASTM D445) less than 12.5 cSt. In particular, neutral and overbased calcium salts of organic acids have been found to increase low temperature high shear viscosity when measured in the CCS (ASTM D5293). These salts which are widely used for their detergency and acid neutralization properties should be avoided altogether or used at a level not exceeding 0.0007 moles of organic calcium salt per 100 grams of lubricant. Where diesel performance is required, for example to lubricate passenger car diesel engines, a calcium salt of an organic acid may be required to control piston deposits. In that circumstance the level of calcium salt should be kept between 0.0004 and 0.0007 moles per 100 grams of lubricant. |