Oil composition for lubricating an EGR equipped diesel engine and an EGR equipped diesel engine comprising same

A method of operating a diesel engine provided with an exhaust gas recirculation system comprising lubricating said engine with a lubricating oil composition comprising:

• a lubricating oil composition comprising:
• (i) a polymeric dispersant booster comprising monomer units of:
• a) 0 to 40 wt. % of one or more ethylenically unsaturated ester compounds of formula (I)
• wherein R is equal to H or CH3,
• R1 represents a linear or branched alkyl group with 1 to 5 carbon atoms,
• R2 and R3 independently represent H or a group of the formula —COOR′, wherein R′ is H or an alkyl group with 1 to 5 carbon atoms,
• b) 10 to 98 wt. % of one or more ethylenically unsaturated ester compounds of formula (II)
• wherein R is equal to H or CH3,
• R4 represents a linear or branched alkyl group with 6 to 15 carbon atoms,
• R5 and R6 independently represent H or a group of the formula —COOR″, wherein R″ is H or an alkyl group with 6 to 15 carbon atoms,
• c) 0 to 30 wt. % of one or more ethylenically unsaturated ester compounds of formula (III)
• wherein R is equal to H or CH3,
• R7 represents a linear or branched alkyl group with 16 to 30 carbon atoms,
• R8 and R9 independently represent H or a group of the formula —COOR′″, wherein R′″ is H or an alkyl group with 16 to 30 carbon atoms,
• d) 0 to 30 wt. % of vinyl monomers,
• e) 7 to 25 wt. % of at least two N-dispersant monomers comprising:
• i) N-vinylpyrrolidinone, in amounts of up to 5 wt. %;
• and
• ii) at least one N-dispersant monomer one selected from the group consisting of dimethylaminopropylacrylamide, dimethylaminoethylacrylamide and tert-butyl aminoethylmethacrylate.
• wherein a)-e) add up to 100 wt.-%;
• and
• (ii) an oil of lubricating viscosity.