Abstract: Provided are novel succinimide compounds obtained by reacting a polyamine having a carbon/nitrogen weight ratio of from 0.85 to 1.25 with a succinic acid compound in a molar ratio to the polyamine of up to 1.40; a process for producing them; a lubricating oil additive containing the compound; and a lubricating oil composition for internal combustion engines which comprises a lube base oil, (a) at least one compound selected from the group consisting of overbased sulfonates, phenates and salicylates with alkaline earth metals, and (b) the succinimide compound, and which has a total base number of from 30 to 150 mg-KOH/g. The composition is for use in internal combustion engines that may discharge a large amount of sulfur oxides (SOx), having the advantage of good corrosion resistance against SOx to be discharged in large quantities.

Abstract: Disclosed are novel succinimide compounds effective in diesel engine lubricating oil for protecting engine parts from being corroded or worn by SOx. An acid compound of formula (I) or (II) is reacted with a polyamine to produce the succinimide compounds, which give an absorption peak (.alpha.-peak) at 1640.+-.cm.sup.-1 and an absorption peak (.beta.-peak) at 1700.+-.10 cm.sup.-1 in the IR spectral pattern with the ratio, .alpha.-peak intensity/.beta.-peak intensity, of being 0.12 or more.[1] ##STR1## R is an alkenyl or alkyl group derived from a C2 to C15 olefinic polymer and having a number-average molecular weight of from 200 to 4000. The succinimide compound is added to base oil along with a metallic detergent-dispersant additives selected from over-based sulfonates, phenates and salicylates of alkaline earth metals to give a lubricating oil composition for diesel engines.

Abstract: Overbased sulfurized alkaline earth metal phenates which are oil soluble, excellent in detergency dispersancy and have high base value, and an effective process for production of said overbased sulfurized alkaline earth metal phenates under conditions providing less sludge and less raw material recovery, and further a lubricating oil additives containing said overbased sulfurized alkaline earth metal phenates as a main ingredient and a lubricating oil composition which comprises said lubricating oil additive compounded in a lubricating oil are disclosed. Since the resulting overbased sulfurized alkaline earth metal phenates have high base value and excellent oil-solubility, they can be effectively utilized as lubricating oil additives.