To provide an environmentally friendly lubricant oil for Diesel-engine having higher cleanability and higher acid neutralization capacity than a boron- containing, ash-free type dispersing agent-containing lubricating oil composition over a long period of time by using a boron-free, ash-free type dispersing agent and also having excellent cleanability and excellent acid neutralization capacity over a long period of time even in a lubricating oil composition having a small sulfate ash content derived from a metallic detergent.
A boron-free lubricating oil composition for Diesel-engine is obtained by incorporating into a lubricating oil base oil of a mineral oil, a synthetic oil and a mixture thereof, (A) 1-12 mass % calcium alkylsalicylate or calcium alkylsalicylate and magnesium alkylsalicylate which meet the relation-ship the ratio of the sulfate ash content value prescribed in JIS K2272 to the total base value measured by the hydrochloric acid method prescribed in JIS K2501 or the total base value measured by the perchloric acid method shows 0.01-0.20 and (B) not less than 0.1 mass % polyalkenyl succinimide in terms of the nitrogen content.
SATO TAKESHI
MIYAHARA KENSAKU
NAGAKARI MITSUHIRO
