PROCESS FOR IMPROVING LUBRICATING QUALITIES OF LOWER

QUALITY BASE OIL

FIELD OF THE INVENTION

This invention is directed to processes for producing an API Group I base oil, a process for improving the lubricating properties of a lower quality base oil, and a process for operating a base oil piant.

BACKGROUND OF THE INVENTION

Improved processes for producing APi Group I base oii by blending lower quality base oii that may not even meet API Group i specifications with a second base oil are needed. There wouid be cost advantages and performance advantages achieved by being able to produce and utilize lower quality base oils that could be biended to meet specifications.

SUMMARY OF THE INVENTION

There is provided a process for producing an AP! Group I base oil,

a, obtaining a lower quality base oil not meeting API Group I specifications, having; i. a saturates level less than 90 weight percent, and ii. one or more suboptirnal properties selected from the group consisting of a viscosity index less than 80, a pour point greater than -10 degrees C, and an Oxidator BN of less than 15 hours; and b. blending the lower quality base oil with a Fischer-Tropsch derived distillate fraction having: i. a Fischer-Tropsch pour point less than -9 degrees C;

Ii. a Fischer-Tropsch viscosity index greater than an amount calculated by the equation: 28 x Ln(Kinematic Viscosity at 100 ⁰ C) + 80; iii. a Fischer-Tropsch Oxidator BN of greater than 20 hours; and c, isolating the API Group I base oil; wherein the API Group I base oil has a viscosity index greater than 95, a pour point less than -7 degrees C, and an Oxidator BN of greater than 9.5

There is provided a process for improving the lubricating properties of a lower quality base oil not meeting API Group I specifications, that is characterized by: a. a saturates level less than 70 weight percent, b. a viscosity index less than 70, and c. an Oxidator BM of less than 6 hours; the process comprising: blending with said lower quality base oil a Fischer- Tropsch derived distillate fraction; wherein an API Group I base oil is

There is provided a process for producing an API Group I base oil, consisting essentially of: (a) selecting a lower quality base oil not meeting API Group I specifications, that is characterized by a saturates level less than 70 weight percent, a viscosity index less than 70, and an Oxidator BN of less than 6 hours; and (b) blending the lower quality base oil with a Group Il base oil and a Fischer-Tropsch derived base oil to make an API Group I base oil.

There is also provided a process for operating a base oil plant, comprising: a. selecting a refinery operating condition to produce a lower quality base oil not meeting API Group ! specifications, that is characterized by: i. a saturates level less than 70 weight percent,

Ii. a viscosity index less than 70, and iii. an Oxidator BN of less than 6 hours;

b. blending the lower quality base oil with a second base oil to make a blended base oil meefinc

BRIEF DESCRIPTION OF THE DRAWING

the plot of Kinematic Viscosity at 100 ⁰ C ₁ in mm ² /s, ity, in wt%; providing the plot of the equation:

:ιc v-2.7

DETAILED DESCRIPTION OF THE INVENTION

The specifications for Lubricating Base Oils are defined in the API Interchange Guidelines (API Pub!

are desired in certain finished lubricant formulations there are specialized packages and individual additives that are designed for use in these ils, and improving one or men such as Vl ₁ sulfur or sy blending can enable the resui used in lubricant formulations unattainable by either

In general, the properties most desired in base oils, however, are high viscosity index, low sulfur, low pour point, and high saturates content.

Achieving the more desired properties can be costly, complicated, and require

significant energy expenditure to produce. We have found that lower quality base oil, not even meeting AP! Group I specifications, can be produced efficiently, and then biended with a second base oil to be brought up to AP! Group I specifications.

The lower quality base oil can be bio-derived, petroleum derived, synthetic, or mixtures thereof. The iower quality base oil will have a low saturates content. For example it can have less than 90 weight percent, less than 70 weight percent, less than 60 weight percent, or even less than 50 weight percent. Saturates, at levels of less than about 95 wt%, are measured by fluorescence indicator adsorption (FIA), The standard method used in the petroleum industry for measuring the quantitative amount of saturates, olefins and aromatics in a hydrocarbon composition is discussed in "Hydrocarbon Types in Liquid Petroleum Products by Fluorescence Indicator Adsorption", ASTM Test No. D 1319-03, updated editorially in June 2008.

The iower quality base oil has one or more other suboptimal properties, which can include low viscosity index, high pour point, and low oxidation stability. Viscosity index (Vl) is an empirical, unitless number indicating the effect of temperature change on the kinematic viscosity of the oil, The iower quality base oil can have a viscosity index less than 100 or less than 90, such as less than 7O ₅ less than 60, or even less than 50. The viscosity index in some embodiments can be even less than 0. The test method used to measure viscosity index is ASTM D 2270-04. The lower quality base oil can have a pour point that is higher than desired, for example greater than -15°C, greater than -10 ⁰ C, or greater than O ¹⁵ C, Pour point is a measurement of the temperature at which a sample of base oil will begin to flow under carefully controlled conditions. One test method used to measure pour point is D 5950 - 02 (Reapproved 2007).

The lower quality base oil can have a low oxidation stability, as determined by measuring the Oxidator BN. The Oxidator BN can be less than 20 hours, less

than 15 hours, less than 8 hours, less than 4 hours, or even less than 2 hours. The Oxidator BN test is described by Stangelaπd et al. in U.S. Patent 3,852,207. The Oxidator BN test measures the resistance to oxidation by means of a Dornte-type oxygen absorption apparatus. See R. W. Dornte Oxidation of White Oils," Industrial and Engineering Chemistry, Vol. 28, page 26, 1938. Normally, the conditions are one atmosphere of pure oxygen at 340 ⁰ F. The results are reported in hours to absorb 1000 ml of 02 by 100 g. of oil. In the Oxidator BN test, 0,8 m! of catalyst is used per 100 grams of oil and an additive package is included in the oil. The catalyst is a mixture of soluble metal naphthenates in kerosene. The mixture of soluble metal naphthenates simulates the average metal analysis of used crankcase oil. The level of metals in the catalyst is as follows: Copper = 8,927 ppm ; Iron ^™ 4,083 ppm ; Lead = 80,208 ppm ; Manganese^ 350ppm ; Tin™ 3565 ppm. The additive package is 80 msflimoles of zinc bispolypropylenephenyldithio-phosphate per 100 grams of oil, or approximately 1.1 grams of OLOA 280. The Oxidator BN test measures the response of a lubricating base oil in a simulated application. High values, or long times to absorb one liter of oxygen, indicate good oxidation stability.

OLOA is an acronym for Oronite Lubricating Oil Additive®, which is a registered trademark of Chevron Oronite.

The lower quality base oil can be produced in a base oil plant under refinery operating conditions that contribute to the properties of the base oil. The most common refining process that can be used for waxy feeds is solvent

Solvent dewaxing is a process often employed in the production of API Group I base oils. Solvent dewaxing employs a dewaxing solvent which assists in the separation of wax from the oil. The solvents employed mix readily with the oil to form a solution but have the effect of decreasing the solubility of the wax in the oil-solvent mixture so that the wax will crystallize out of the oil at a

higher temperature. This, in turn, means that oils of lower pour point can be more readily produced with only a moderate degree of cooling in the process since the pour point of the dewaxecl oil is dependent both upon the solubility of the wax in the oil and the temperature at which the dewaxing is performed. Thus, a reduction in the solubility of the wax means either that lower pour point oils may be produced at given operating temperatures or that a given pour point obtained at higher operating temperatures. Generally, ketones will be used for this purpose, with acetone, methyl ethyl ketone (MEK) ₁ methyl propyl ketones, methyl butyl ketones especially methyl iso-butyl ketone, being frequently selected.

The ketone may be used by itself or, more preferably, with an aromatic solvent such as benzene, toluene or petroleum naphtha which increases the solubiiity of the oil but diminishes the solubility of the wax. The amount of solvent used will be dependent upon other factors such as the pour point desired for the dewaxed product, the wax content of the feedstock (amount and type of wax), viscosity of the dewaxed oil, the design operating temperature of the system and the amount, if any, of autorefrigerant used.

In one embodiment of solvent dewaxing there is a chilling zone, where wax is precipitated from the oil to form a waxy slurry and the so formed slurry is further chilled down to the wax filtration temperature by stage-wise contact with a liquified gas such as propylene, or other autorefrigerant, which is injected into the liquid layer. An autorefrigerant, as used herein, is equivalent to a liquefied gas. Autorefπgeratrøn is a three step process comprised in its most basic form of (a) condensing gases by cooling, (b) separating out the liquefied gases, and (c) evaporating the liquefied gases to provide cooling. The presence of other compounds within the liquefied gases such as dissolved gases (e.g., hydrogen), or the presence of an added substance such as methanol to lower the freezing point, or the use of an intermediary

stream to transfer heat from the condensing stream to the evaporating stream do not alter the fundamental fact that an autorefrigeratioπ stage exists if the three basic steps (a), (b) and (c) are present. Those three steps can be present two or more times (i.e. two or more stages). An autαrefrigeratϊαn stage is characterized by a temperature range at which condensation of gases takes piace at the pressure at which evaporation of the liquefied acid gases takes place.

The amount of solvent used in solvent dewaxing may be determined by appropriate experience or experiment but as a genera! guide will be from 0,5:1 to 4:1 (solventoil) based on the weight of the oil feed. Refining costs may be reduced and safety is improved with lower solventoii ratios of 0.5:1 to 2:1. As the lower quality base oil can have a higher pour point, there is more flexibility in selecting the choice of solvents and the solventoii ratio.

in the past the choice of solvents was restricted to those that were less sulfur- selective or to those that had lower solubility of the wax in the oil-solvent mixture. The restricted choices of solvents were necessary so that the amount of sulfur in the separated oil was kept at a lower level and the pour point was acceptably low. The choice of solvents can now be expanded and selected for other features such as low cost, environmental benefits, energy

Solvents may be selected having different sulfur solubility. One method for measuring the sulfur solubility of a solvents is by the following method. 10 mg of sulfur powder is added to each solvent and agitated for 10 minutes. If the sulfur powder dissolves completely, then an additional 10 mg of sulfur powder is added, and this procedure is conducted repeatedly. When a portion of

added sulfur powder does not dissolve, the non-dissolved sulfur is recovered through filtration with a filter paper, and the mass of the filtered sulfur is measured. The sulfur solubility of the solvent is calculated from the mass of the non-dissolved sulfur. The sulfur solubilities of some example tested solvents are shown below in Table 1.

TABLE 1

Non-dissolved Sulfur sol

No. Solvent sulfur (mg) (mM)

1 Benzene SOO 87,9

2 Fluorobenzene 850 83.0

3 Toluene 860 84.0

4 Trifluorotoluene 800 78.1

5 Xylene 790 77.1

6 Cyclohexane 950 92, S

7 Tetrahydrofurane (THF) 490 47.9

8 2 -methyl tetrahydrofurane 450 43.9

(2-MeTHF)

Ct Cyc1ohexanone 80 7.3

IO Ethanol (EtOH) 9 0,9

11 Isopropanol .10 1.0

12 Dimethyl carbonate (DMC) 8 0.8

As shown in Table 1 , a solvent having a sulfur solubility greater than or equal to 50 mM, for example, would include cyclohexane, xylene, trifluorotoluene, toluene, fluorobenzene, and benzene.

Second Base Oil

The lower quality base oil is blended with a second, much higher quality, base oil. The second base oil can have a very high viscosity index. It can also have a lower kinematic viscosity than the lower quality base oil that it is blended with. Kinematic viscosity is a measurement of the resistance to flow of a fluid under gravity. Many base oils, finished lubricants made from them, and the correct operation of equipment depends upon the appropriate viscosity of the fluid being used. Kinematic viscosity is measured by ASTM D 445-08.

In some embodiments the second base oil will be Fsscher-Tropsch derived. Tischer-Tropsch derived" means that the material originates from or is produced at some stage by a Fsscher-Tropsch synthesis process which produces Fischer-Tropsch synthesis products. The Fischer-Tropsch synthesis products can be obtained by well-known processes such as, for example, the commercial SASOL® Slurry Phase Fischer-Tropsch technology, the commercial SHELL® Middle Distillate Synthesis (SMDS) Process, or by the non-commercial EXXON® Advanced Gas Conversion (AGC-21) process. Details of these processes and others are described in, for example, EP-A- 778959, EP-A-668342; U.S. Patent Nos. 4,943,672, 5,059,299, 5,733,839, and RE39073 ; and US Published Application No. 2005/02278Be ₁ WO-A- 9934917, WO-A-9920720 and WO-A-05107935. The Fischer-Tropsch synthesis product usually comprises hydrocarbons having 1 to 100, or even more than 100 carbon atoms, and typically Includes paraffins, olefins and oxygenated products. Fischer Tropsch Is a viable process to generate clean alternative hydrocarbon products.

Fsscher-Tropsch derived base oils are described for example in US20040258287, US20040256288, US20040159582, US701825, US 20050139513, US7282134, US200600018724, US6700027, US8702937,

US6805206. US20060289337, and US20060201851. The processes used to make these base oils can include hydracracking, hydroisornerizing, oiigomerizing, catalytic and/or solvent dewaxing, separating, vacuum distilling, and hydrofinishing.

The Fischer-Tropsch derived base oil can have a viscosity index greater than an amount calculated by the equation: 28 x Ln{Kinematic Viscosity at 100 ⁰ C) +80. In some embodiments, it will have a viscosity index greater than an amount calculated by the equation: 28 x Ln(Kinernatic Viscosity at 100 ⁰ C) +90, or greater than an amount calculated by the equation: 28 x Ln (Kinematic Viscosity at 100 ⁰ C) +95.

The second base oil has good oxidation stability. In some embodiments it can have an Oxidator BN greater than 15 hours, greater than 20 hours, greater than 25 hours, or greater than 35 hours. The Oxidator BN of the second base oil will typically be less than about 75 hours.

The second base oil can be one of several different grades. Base oils recovered from a vacuum distillation tower can include a range of base oil grades, such as XXLN, XLN, LN, MN, and HN. An XXLN grade of base oil when referred to in this disclosure is a base oil having a kinematic viscosity at 100 ⁰ C between about 1.5 mm ² /s and about 2.3 mm ² /s. An XLN grade of base oil will have a kinematic viscosity at 100 ⁰ C between about 2.3 mm ² /s and about 3.5 mm ² /s. A LN grade of base oil will have a kinematic viscosity at 100 ⁰ C between about 3.5 mm ² /s and about 5,5 mm ² /s. A MN grade of base oil will have a kinematic viscosity at 100 ^c C between about 5.5 mm ² /s and 10 mm ² /s. A HN grade of base oil will have a kinematic viscosity at 100 ⁰ C above 10 rnm ² /s. Generally, the kinematic viscosity of a HN grade of base oil at 1OQ ⁰ C will be between about 10.0 mrrs ² /s and about 30.0 mm ² /s, or between about 15.0 mm ² /s and about 30.0 mm ² /s.

Base oils produced by hydroprocessing tend to produce higher amounts of lower viscosity products, due to hydrocracking of heavier molecules in the feed to the process. These oils can be of very high quality, but the base oil grades of XXLN, XLN, and LN will be produced in higher yields than the MN and HN grades. In one embodiment the lower quality base oil is a MN or HN grade and the second base oil is a XXLN, XLN ₁ or LN grade.

In one embodiment, the second base oil is a Fischer-Tropsch derived distillate fraction having between 90 and 99 wt% paraffinic carbon and between 2 and 10 wt% naphthenic carbon. Paraffinic carbon and naphthenic carbon are determined by n-d-M analysis (ASTM D 3238-95 (Re-approved 2005)}.

Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FlMS). In FIMS, the base oil is characterized as afkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations, When olefins are present in significant amounts, they would be identified as 1- unsaturations. The total of the 1 -unsaturations, 2-unsaturations, 3- unsaturations, 4-unsaturations, 5-unsaturations, and δ-unsatu rations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycioparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycioparaffinic functionality, The total weight percent of molecules with cycioparaffinic functionality is the sum of the weight percent of molecules with monocyclopraffinic functionality and the weight percent of molecules with muiticycloparaffinic functionality.

Molecules with cycioparaffinic functionality mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused muiticyciic saturated hydrocarbon group. The cycioparaffinic group can be optionally substituted with one or more, such as one to three, substituents.

Representative examples include, but are not limited to, cyciopropyi, cyciobutyl, cyclohexyl, cyclopentyl, cycloheptyl, decahydronaphthalβne, octahydropentalene, (pentadecan-6-yl}cyclohexane, 3,7,10- tricyclohexylpentadecane, decahydro-1-(pentadecan-6-y!)naphthalene, and the like.

Molecules with monocycloparaffinic functionality mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons. The cycioparaffinic group

can be optionally substituted or more, such as one to three, substituents. Representative ies include, but are not limited to, cyclopropyl, CyClObUtVl ₁ opβntyl cycloheptyi, (pentadecan-β- yl)cyclohexane, and the

Molecules with multicycloparaffinic functionality mean any molecule that is a fused muiticyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused muiticyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons. The fused muiticyclic saturated hydrocarbon ring group often is of two fused rings. The cycloparaffinic group can be optionally substituted with one or more, such as one to three, substituents. Representative examples include, but are not limited to,

i-1 ~( 3-yl the like.

In one embodiment the second base oil is a Fischer-Tropsch derived distillate fraction having greater than 10 wt% total molecules with cycloparaffinic functionality and a high ratio of molecules with monocycloparaffinic functionality to molecules with multicycioparaffinic functionality. The ratio of cycloparaffins can be greater than 3, greater than 5, greater than 10, greater than 15, or greater than 20. Processes to produce these types of base oils are taught in US7282134 and US20060289337, The processes include dewaxing a Fischer-Tropsch wax under selected conditions using a shape

Lu^ricanlBase_Oi!_Bjend

The blending of the Sower quality base oil produces API Group I base oil The AP at least 5 wt%.

such as at least 10 wt%, based on the total composition of the lower quality base oil. The API Group I base oil comprises less than 90 wt% of the lower quality base oil. The API Group I base oil comprises between 5 and 80 wt%, such as between 10 and 50 wt% or between 20 and 40 wt%, of the second

The APf Group I base oil can be of excellent quality, including having a high viscosity index, low pour point, and excellent oxidation stability. Additionally it can have a low CCS viscosity or a low Noack volatility. The AP! Group I base oil can have a viscosity index greater than 95, such as greater than 100, or even greater than 105. The API Group I base oil can have a pour point less than ~5°C, such as less than ~7 ^ϋ C , less than -10 ⁰ C, less than -15 ⁰ C, or even less than -20 ⁰ C. The API Group f base oil can have an Oxidator BN greater than 8 hours, for example greater than 9.S ₁ greater than 11 , or greater than 12 hours.

In one embodiment the API Group I base oil has a low CCS Viscosity. It can be a LN grade with a CCS Viscosity at -25 ⁰ C of less than 4,000 cP. It can be a MN grade with a CCS Viscosity at ~20°C of less than 4,000 cP, or it can be a HN grade with a CCS Viscosity at -10 ⁰ C of less than 4,000 cP . CCS

Viscosity is a test used to measure the vϊscornetric properties of oils under tow temperature and high shear. A low CCS Viscosity makes an oil very useful in a number of finished lubricants, including multigrade engine oils, The test method to determine CCS Viscosity is ASTM D 5293-04. Results are reported in centipoise, cP.

In one embodiment the API Group I base oil has a now Noack volatility. Noack volatility is usually tested according to ASTM D5800-05 Procedure B. Noack volatility of base oils generally increases as the kinematic viscosity decreases. The lower the Noack volatility, the lower the tendency of base oil and formulated oils to volatilize in service. The API Group I base oil can have

_ Ή _

a Noack volatility less than an amount calculated by the equation: 2000 x (Kinematic Viscosity at 100 ⁰ C) ^'2'7 .

Finished Lubricants:

Finished iubricants comprise a lubricant base oil and at feast one additive. The lubricant base oil can be the Group I base oil. Lubricant base oils are the most important component of finished lubricants, generally comprising greater than 70% of the finished lubricants. Finished lubricants may be used for example, in automobiles, diesel engines, axles, transmissions, and industrial applications. Finished lubricants must meet the specifications for their intended application as defined by the concerned governing organization.

Additives which may be blended with the lubricant base oil blend to provide a finished lubricant composition include those which are intended to improve select properties of the finished lubricant. Typical additives include, for example, pour point depressants, anti-wear additives, EP agents, detergents, dispersanfs, antioxidants, viscosity index improvers, viscosity modifiers, friction modifiers, demulsifiers, anfifoaming agents, corrosion inhibitors, rust inhibitors, seal swell agents, emulsifiers. wetting agents, lubricity improvers, metal deactivators, gelling agents, tackiness agents, bactericides, fungicides, fluid-loss additives, colorants, and the like.

Typically, the total amount of additives in the finished lubricant will be approximately 0,1 to about 30 weight percent of the finished lubricant. However, since the lubricating base oils of the present invention have excellent properties including excellent oxidation stability, low wear, high viscosity index, low volatility, good low temperature properties, good additive solubility, and good elastomer compatibility, a lower amount of additives may be required to meet the specifications for the finished lubricant than is typically required with base oils made by other processes. The use of additives in

formulating finished lubricants is wet known to those of skill in the art.

EXAMPLES

1 :

Two samples of base oils not meeting AP! group I specifications had the in Table I.

Table I

Three samples of Fischer-Tropsch derived base oils were made by hydrcHSomerϊzing a hydrotreated Fischer-Tropsch wax, followed by hydrofiπishing and fractionation. All three of these samples were distillate fractions. As used in this disclosure, the term "distillate fraction" or "distillate" refers to a side stream product recovered either from an atmospheric fractionation column or from a vacuum column as opposed to the "bottoms" which represents the residual higher boiling fraction recovered from the bottom of the column. The properties of the three Fischer-Tropsch derived base oils are summarized in Table If.

The very high saturates were measured more accurately by high pressure Isquid chromatography (HPLC) The sample ss dissolved in n-hexane and any

concentrated to a known volume, a portion is quantitatively injected into the HPLC, and the separation is monitored with a refractive index (Rl) detector The saturates are eluted wrth n-hexane and collected The flow of n-hexane is reversed and the aromatics are eluted and collected When the aromatics are completely elufed as indicated by the Rl detector, the mobile phase is changed to a 1 1 mixture of acetone and methylene chloride and the polars are then eluted and collected The solvents are evaporated, the fractions are weighed and the weight percent distribution in the original sample is calculated The fractions may be used for further analyses (MS, GC, NMR, etc )

Note that all three of these Fischer-Tropsch base oils had very high viscosity indexes, generally such that X, in the equation V! = 28 x Ln(Kιπematιc Viscosity at 100 ⁰ C) +X, is greater than 90 The LFTBO and MFTBO had

values of X that are especially desired, greater than 107 and greater than 104

Example 2:

The petroleum derived base oils not meeting API Group blended with the Fischer-Tropsch derived base oils of E proportions to produce LM, MN, and HN grade API base oils having improved properties. The blend compositions and are summarized

Table

Note that these blends were a!! AP! Group I base oils having viscosity indexes greater than 95, pour points less than -7 degrees C, and Oxidator BNs greater than 9.5 hours. All three blends had a Noack Volatility less than an amount calculated by the equation: 2000 x (Kinematic Viscosity at 100 ⁰ C) ^{"2 7} . The plot of this equation is shown in FIG. 1. The LN grade "110N" example had an espβciafiy low CCS Viscosity at ~25°C, of less than 4,000 CP. The MN grade "220N" and "230N" examples had excellent CCS Viscosities at ~2QX of less than 4,000 cP; and the HN ^" '575N" example also had an excellent CCS Viscosity at -10 ⁰ C of less than 4,000 cP. These would be excellent base oils

All three of these blends were examples of a process for producinc

Group I base oil consisting essentially of or consisting of: a) selecting a lower quality base oil not meeting AP! Group \ specifications, that I

70, and an Oxidator BN of less than δ hours, b) blending the ower quality base oil with a Group H base oil and a Fischer-Tropsch til to make an API Group I base oil.

Example 3:

Blends of the petroleum derived base oils not meetint specifications were blended, for comparison, with conventii derived Chevron API Group Il base oils in different proportions to produce LN, \, and HN grade API Group I base oils having improved

Table IV

These comparison blends did not have the high VI and hsgh Oxidator BN of the AP! Group I base oils of our invention

Al! of the publications, patents and patent applications cited in this application are herein incorporated by reference in their entirety to the same extent as if the disclosure of each individual publication, patent application or patent was specifically and individually indicated to be incorporated by reference in its

Many modifications of the exemplary embodiments of the invention disclosed above will readily occur to those skilied in the art. Accordingly, the invention is to be construed as including all structure and methods that fall within the scope of the appended claims.