Abstract: A method of improving the low temperature properties of a fuel oil and minor amounts of (a) at least one polar nitrogen compound effective and (b) at least one polyamine detergent is disclosed. The method involves adding to the composition (c) at least one acidic organic species.

Abstract: An additive concentrate comprises a lubricity enhancer dissolved in a solvent. The lubricity enhancer comprises from 10 to 90% by weight of the concentrate and is a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-n-butylamine. The concentrates have excellent low temperature stability.

Abstract: A salt formed by the reaction of a carboxylic acid with a hydrocarbyl derivative of pyridine. The salts are effective lubricity enhancers when added to low sulphur content fuels and are soluble at low temperatures.

Abstract: A fuel oil composition comprises a fuel oil in a major amount, which fuel oil has a mass % against n-alkane carbon number distribution curve characterised by: (i) a maximum negative gradient from carbon number 18 to carbon number 26 that is less than ?0.30; and (ii) a ratio of the mass of n-alkanes of carbon number greater than 22 to the mass of n-alkanes from carbon number 18 to carbon number 21 that does not exceed 0.

Abstract: An additive composition comprises at least one colloidal metal compound or metallic species and a stabilising component, wherein the stabilising component comprises the product obtainable by the condensation reaction between: (i) at least one aldehyde or ketone or reactive equivalent thereof, and (ii) at least one compound comprising one or more aromatic moieties bearing at least one hydroxyl group and at least one further substituent chosen from a hydrocarbyl group, —COOR1 or COR1, wherein R1 represents hydrogen or a hydrocarbyl group. The composition may further include at least one lubricity enhancer. Compositions of the invention tend to resist haziness, cloudiness and phase separation at relatively low and relatively high temperatures, and in the presence of lubricity enhancers and fatty acid methyl esters (FAME).

Abstract: This invention relates to fuel oil, especially middle distillate fuel oil, compositions comprising middle distillate fuel oil and incorporated therein an incorporated therein an additive composition comprising (a) at least one fuel-soluble or fuel-dispersible neutral alkaline earth metal compound and/or at least one fuel-soluble or fuel-dispersible neutral alkali metal compound, and (b) at least one fuel-soluble or fuel-dispersible transition metal compound, characterised in that the fuel oil composition contains at most 0.05 mass % of sulfur, the total metal content derived from (a) and (b) in the fuel oil composition is at most 50 ppm by mass, and the mass proportion of (a) to (b), based on metal content, is in the range of from 1:99 to 99:1.

Abstract: An additive comprising an oil-soluble stable free radical, such as a nitroxide, or a precursor therefor, is used in a fuel oil to reduce, on combustion of the fuel oil, one or more of particulate emissions, hydrocarbon emissions, carbon monoxide emissions, and oxides of nitrogen emissions.