Oil additives and compositions

A fuel oil composition comprising a fuel oil and an additive composition comprising:

• (a) an oil soluble ethylene copolymer having, in addition to units derived from ethylene, units of the formula
• —CH2—CRR1— I
• and units of the formula
• —CH2—CRR2— II
• the total molar proportion of units of the formulae I and II in the copolymer being less than 10%, wherein each R independently represents H or CH3, and each R1 and R2 independently represents a group of the formula COOR3 or OOCR3, wherein each R3 independently represents alkyl or alkenyl having 4 to 10 carbon atoms provided that the units of the formula I are different from the units of the formula II or
• (b) comprising
• (i) an oil-soluble ethylene copolymer having, in addition to units derived from ethylene, less than 10 molar per cent of units of the formula
• —CH2—CRR1— I
• and (ii) an oil-soluble ethylene copolymer having, in addition to units derived from ethylene, less than 10 molar per cent of units of the formula
• —CH2—CRR2— II
• wherein R, R1, and R2 have the meanings given above, provided that R3 in COOR3 represents alkyl or alkenyl having 4 to 10 carbon atoms, and provided that copolymer (i) differs from copolymer (ii) by at least 2000 in number average molecular weights.