Use of a paraffinic gasoil

1. A method for reducing build up of deposits in a high-pressure Exhaust Gas Recirculation (EGR) system of a compression ignition internal combustion engine, the method comprising the steps of:

providing a compression ignition internal combustion engine having a high-pressure EGR system and a particulate filter, wherein the particulate filter is positioned downstream of the high pressure EGR;

introducing into the engine a diesel fuel composition comprising:

a paraffinic gasoil present at a level of from 50% v/v to 100% v/v, based on the total diesel fuel composition,

wherein the paraffinic gasoil is selected from a Fischer-Tropsch derived gasoil comprising no more than 3% w/w of cycloparaffins, by weight of the Fischer-Tropsch derived gasoil and having a kinematic viscosity in a range from 2.0 to 5.0 mm 2 /s at 40° C., a density in a range from 0.775 to 0.785 g/cm 3 , an aromatics content below 0.1% w/w and a cetane number from 70 to 77, and a hydrotreated vegetable oil (HVO) derived gasoil, and mixtures thereof; and

combusting the diesel fuel composition;

wherein deposits in the EGR system after the fuel composition has been combusted in the compression ignition internal combustion engine for 24 hours continuously, at 2500 rpm and 5 kW test condition and at an engine coolant temperature controlled to 37° C., are reduced by 10% or more compared to the build up of deposits in an EGR system caused by an analogous fuel formulation which does not contain a paraffinic gasoil.

2. The method of claim 1 wherein the paraffinic gasoil comprises greater than 95wt % paraffins, based on the total weight of the paraffinic gasoil.

3. The method of claim 1 wherein the paraffinic gasoil comprises greater than 98wt % paraffins, based on the total weight of the paraffinic gasoil.

4. The method of claim 1 wherein the diesel fuel composition additionally comprises a diesel base fuel.

5. The method of claim 1 wherein the paraffinic gasoil is present in the diesel fuel composition at a level in the range from 80% v/v to 100% v/v, based on the total diesel fuel composition.

6. The method of claim 1 wherein the paraffinic gasoil is present in the diesel fuel composition at a level in a range from 90% v/v to 100% v/v, based on the total diesel fuel composition.

7. The method of claim 1 wherein the Fischer-Tropsch derived gasoil has a kinematic viscosity in the range from 2.5 to 5.0 mm 2 /s at 40° C.

8. The method of claim 1 wherein the Fischer-Tropsch derived gasoil comprises no more than 2% w/w of cycloparaffins, by weight of the Fischer-Tropsch derived gasoil.

9. The method of claim 1 wherein the Fischer-Tropsch derived gasoil comprises no more than 1% w/w of cycloparaffins, by weight of the Fischer-Tropsch derived gasoil.

10. The method of claim 1 wherein the build up of deposits is reduced in one or more of the EGR outlet pipe, EGR valve, EGR cooler or EGR housing of the high-pressure Exhaust Gas Recirculation (EGR) system.

11. The method of claim 1 wherein the build up of deposits is reduced in the EGR cooler of the high-pressure Exhaust Gas Recirculation (EGR) system.