Lubricant composition for use the reduction of piston ring fouling in an internal combustion engine

Abstract

The present invention relates to a lubricant composition comprising a base oil or base oil blend and one or more additives, wherein the lubricant composition has a kinematic viscosity at 100° C. of more than 5.0 mm 2 /s (cSt), a cold cranking simulated dynamic viscosity at −15° C. according to ASTM D 5293 of less than 9500 mPas (cP) and a mini rotary viscosity test value of less than 60000 mPas at −20° C. according to ASTM D 4684, and wherein the base oil or base oil blend has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon fraction and comprises a continuous series of isoparaffins having n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and 35, suitable for the reduction of piston ring fouling in an internal combustion engine.

1 . A lubricant composition comprising a base oil or base oil blend, saturated cyclic hydrocarbons in an amount of 5 to 10 wt %, based on total lubricant composition, and one or more additives, and having a kinematic viscosity at 100° C. of more than 5.0 mm 2 /s (cSt), a cold cranking simulated dynamic viscosity at −15° C. according to ASTM D 5293 of less than 9500 mPas (cP) and a mini rotary viscosity test value of less than 60000 mPas at −20° C. according to ASTM D 4684, and wherein the base oil or base oil blend has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon fraction and comprises a continuous series of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and 35, having a Top Groove fill of below 50% vol. according to the Nissan TD25 Detergency Test (Japanese Automobile Standards Organization (JASO) M336: 1998). 
   
   
       2 . A lubricant composition according to  claim 1 , having a residual carbon content of less than 4.8% wt. according to the Nissan TD25 Detergency Test (Japanese Automobile Standards Organization (JASO) M336: 1998). 
   
   
       3 . A lubricant composition according to  claim 1  or  2 , wherein the base oil or base oil blend has a kinematic viscosity at 100° C. of from 3 to 25 mm 2 /s. 
   
   
       4 . A lubricant composition according to  claim 1 , wherein the base oil has a pour point of less than −39° C. and a kinematic viscosity at 100° C. of between 3.8 and 8.5 mm 2 /s (cSt), and wherein the lubricant composition has a kinematic viscosity at 100° C. of between 9.3 and 12.5 mm 2 /s (cSt). 
   
   
       5 . A lubricant composition according to  claim 1 , wherein the lubricant composition comprises less than 10 wt % of an additional base oil not derived from a Fischer-Tropsch process. 
   
   
       6 . A lubricant composition according to  claim 1 , wherein the lubricant composition comprises no additional base oil. 
   
   
       7 . A lubricant composition according to  claim 1 , wherein the base oil or base oil blend comprises at least 98 wt % saturates. 
   
   
       8 . A lubricant composition according to  claim 7 , wherein the saturates fraction comprises between 10 and 40 wt % of cyclo-paraffins. 
   
   
       9 . A method of reducing piston ring fouling in an internal combustion engine comprising using in said engine a lubricant composition comprising a base oil or base oil blend, saturated cyclic hydrocarbons in an amount 5 to 10 wt %, based on the total lubricant, and one or more additives, and having a kinematic viscosity at 100° C. of more than 5.0 mm 2 /s (cSt), a cold cranking simulated dynamic viscosity at −15 ° C. according to ASTM D 5293 of less than 9500 mPas (cP) and a mini rotary viscosity test value of less than 60000 mPas at −20° C. according to ASTM D 4684, and wherein the base oil or base oil blend has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon fraction and comprises a continuous series of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and 35. 
   
   
       10 . A method according to  claim 9 , wherein the base oil or base oil blend is obtainable from a process comprising the following steps:
 (a) hydrocracking/hydroisomerisating a Fischer-Tropsch product having a weight ratio of compounds having at least 60 or more carbon atoms and compounds having at least 30 carbon atoms of at least 0.2 and wherein at least 30 wt % of compounds in the Fischer-Tropsch product have at least 30 carbon atoms,   (b) separating the product of step (a) into at least one or more fuel fractions and a base oil precursor fraction, and   (c) performing a catalytic dewaxing step to the base oil precursor fraction obtained in step (b), and optionally   (d) separating the products obtained in step (c) into at least one or more base oil fractions, and a lower boiling fraction.   
   
   
       11 . A method according to  claim 9 , wherein the Fischer-Tropsch product used in step (a) has at least 50 wt %, and more preferably at least 55 wt % of compounds having at least 30 carbon atoms and wherein the weight ratio of compounds having at least 60 or more carbon atoms and compounds having at least 30 carbon atoms of the Fischer-Tropsch product is at least 0.4 and wherein the Fischer-Tropsch product comprises a C 20 + fraction having an ASF-alpha value (Anderson-Schulz-Flory chain growth factor) of at least 0.925. 
   
   
       12 . A method of lubricating a compression-ignited internal combustion engine comprising operating the engine and lubricating the engine with a lubricating oil composition comprising a base oil or base oil blend, saturated cyclic hydrocarbons in an amount 5 to 10 wt %, based on the total lubricant, and one or more additives, wherein the lubricant composition has a kinematic viscosity at 100° C. of more than 5.0 mm 2 /s (cSt), a cold cranking simulated dynamic viscosity at −15° C. according to ASTM D 5293 of less than 9500 mPas (cP) and a mini rotary viscosity test value of less than 60000 mPas at −20° C. according to ASTM D 4684, and wherein the base oil or base oil blend has been obtained from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon fraction and comprises a continuous series of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and 35. 
   
   
       13 . (canceled)