NOVELTY - An additive contains a dicarbonyl-containing compound.    USE - Additive is used for oil, such as base oil used in lubricating oil (claimed), and fuel oil of biodiesel fuel. Can also be used for engine oil, automatic-transmission oil, continuously-variable transmission oil, gear oil, power steering oil, shock absorber oil, turbine oil, hydraulic oil, refrigeration oil, rolling oil, bearing oil, lubricating oil used for metal processing, sliding face oil, and grease, as solid lubricant used for reducing friction and abrasion of plastics, fibers, and recording medium, for coating materials, films, and inks, and for protective-covering layers, toner cleaning components, optical fibers, lithographic printing original plates, image-receiving sheets, optical drop cables, polarizers, endoscopes, and optical films. The sliding components using the lubricant oil include plastic gearwheels, bearings, cams, and thermal recording medium.    ADVANTAGE - The additive is capable of imparting oils with excellent wear resistance and friction resistance.    DETAILED DESCRIPTION - An additive contains a dicarbonyl-containing compound of formula: (A) m-W'-(B') n.    m=0-4;    n,m+n=2-6;    W'=(m+n)-valent group obtained by removing (m+n) hydrogen atoms on carbon atom of compound chosen from 2-20C hydrocarbon, 4-20C ether, 3-20C amine, 4-20C sulfide, and 4-20C disulfide;    A=hydroxy or amino;    B'=group of formula (a);    a=0 or 1;    X=oxygen or NH;    Y'=OR 1 or NHR 2;    R 1,R 2=optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted cycloalkyl, or optionally substituted cycloalkenyl;    Z 1 or Z 2=H, with the other being -NR 3R 4, -N=CR 5R 6 or group of formula (b);    R 3,R 4=H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted cycloalkyl, optionally substituted cycloalkenyl, optionally substituted alkanoyl, optionally substituted alkenoyl, optionally substituted aroyl, optionally substituted cycloalkylcarbonyl, optionally substituted alkoxycarbonyl, optionally substituted alkenyloxycarbonyl, optionally substituted aryloxycarbonyl, optionally substituted cycloalkyloxycarbonyl, or R 3 and R 4 may combine to form nitrogen-containing heterocyclic ring group having substituent grouping with nitrogen atom;    R 5,R 6=H, optionally substituted alkyl, optionally substituted alkenyl, or R 5 and R 6 may combine to form optionally substituted cycloalkylidene grouping with carbon atom;and    R 7,R 8=H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted cycloalkenyl, optionally substituted alkanoyl, optionally substituted alkenoyl, optionally substituted cycloalkylcarbonyl or optionally substituted aroyl, or R 7 and R 8 may combine to form aromatic ring optionally substituted having optionally substituted cycloalkane, or substituent grouping with adjacent two carbon atoms.    An INDEPENDENT CLAIM is included for ester compound of formula: (HO) ma-W'a-(B'a) na.    ma=0-2, preferably 0;    na,ma+na=2-4;    W'a=(ma+na)-valent group obtained by removing (ma+na) hydrogen atom on carbon atom from 2-10C alkane;    B'a=group of formula (c);    b=0 or 1;    Y'a=-OR' 1;    R' 1=optionally substituted 1-20C alkyl or optionally substituted 1-20C alkenyl, preferably optionally substituted 12-20C alkyl or optionally substituted 12-20C alkenyl;and    Za 1 or Za 2=H, with other being phthalimide.