PURPOSE: To provide a gel-free liquid crankcase lubricating oil additive concentrate having a storage stability which comprises a dilute oil, an ashless dispersant and an effective amount of a viscosity index inprover.

CONSTITUTION: This concentrate comprises (A) a dilute oil comprising a mineral oil and/or a synthetic oil, etc., (B) an ashless dispersant comprising, preferably, polyethylene polyamine tetrathylenepentamine, and (C) an effective amount of a viscosity index inprover comprising, preferably, succinic acid imide substituted by a polyisobutenyl group having a number average molecular weight of form 800 to 5,000, an olefin hydrocarbon polymer functionalized with a vinyl monomer such as N-vinyl pyrrolidone, etc.