U.S. patent application Ser. No. 10/743,932, filed Dec. 23, 2003, teaches a finished lubricant that has less than 8 weight percent VI improver made having a lubricating base oil made from Fischer Tropsch wax having particularly desired aromatic and cycloparaffinic molecular composition and at least one lubricant additive. This application, however, does not teach a lower ash lubricating oil containing no viscosity index improver that has a low cold cranking simulator viscosity.
U.S. patent application Ser. No. 10/949,779, filed Sep. 23, 2004, teaches a multigrade engine oil comprising: (a) a Fischer-Tropsch base oil characterized by a kinematic viscosity between about 2.5 and about 8 cSt at 100° C., and having a desired composition of cycloparaffin molecules; (b) a pour point depressing base oil blending component; and (c) an additive package designed to meet the specifications for ILSAC GF-3; and (d) no additional pour point depressant additive or viscosity index improver. Nothing is taught about blending lower ash lubricating oil suitable for use in a natural gas engine without any viscosity index improver and having a low cold cranking simulator viscosity.
PCT Applications WO 2004/053030 and PCT Application WO2004/033606 teach finished lubricants made using base oils made from Fischer-Tropsch wax that have high viscosity indexes and low cold cranking simulator viscosities. Nothing is taught about blending lower ash lubricating oils suitable for use in natural gas engines without any viscosity index improver.
Lower ash lubricating oil suitable for use in natural gas engines with improved cold crank properties over current SAE 40 oils is desired. In addition, customers want lower ash lubricating oils with better low temperature properties meeting SAE 15W-40 specifications. Most current natural gas engine oils (NGEO) meeting SAE 15W-40 specifications, for example, require the addition of viscosity index improvers that may shear in use. In addition, some natural gas original equipment manufacturers (OEMs) require that no conventional petroleum derived bright stock be used in the natural gas engine oil, so blends with good viscometric properties without conventional petroleum derived bright stock are preferred.