Lubricating oil composition

Abstract

A molybdenum-free lubricating oil composition exhibiting improved fuel economy and fuel economy retention properties, which comprises: (a) a major amount of base stock selected from the group consisting of one or more Group IV or Group V oils and mixtures thereof, and mixtures containing one or more Group III oils and at least one Group IV and/or Group V oils, the base stock having a NOACK volatility of 12% or less; and; (b) at least one calcium detergent; and (c) 0.2 to 2.0 wt. % of an organic friction modifier, wherein the composition has a NOACK volatility of about 12 wt. % or less and contains from about 0.058 to 0.58 wt. % calcium from the calcium detergent.

Description

[0001] This is a Continuation-in-Part of U.S. patent application Ser. No. 09/356,262, filed Jul. 16, 1999.

[0002] The present invention relates to lubricating oil compositions. More particularly, the present invention relates to lubricating oil compositions, which exhibit improvements in economy and fuel economy retention properties without the need for organo molybdenum additives and which have low volatility.

BACKGROUND OF THE INVENTION

[0003] It is well known that molybdenum provides enhanced fuel economy when used in lubricants for gasoline or diesel fueled engines, including both short and long term fuel economy (i.e., fuel economy retention properties). The prior proposals typically use molybdenum at levels greater than 350 ppm up to 2,000 ppm in additive packages, which contain one or more detergents, anti-wear agents, dispersants, friction modifiers, and the like.

[0004] The present inventors have found that fuel economy and fuel economy retention properties can be improved to meet the requirements present motor oil certifications, such as ILSAC GF-3 standards (International Lubricants Standardization and Approval Committee), without the use of molybdenum which is commonly used in conventional additive packages, thus providing a less expensive lubricating oil composition. It has further been found that, with such molybdenum-free compositions, viscosity increases upon use of the lubricating oil can be minimized by properly selecting the base stock(s) with which the lubricating oil composition is formulated.

SUMMARY OF THE INVENTION

[0005] The present invention concerns a lubricating oil composition which exhibits improved fuel economy and fuel economy retention properties, the composition comprising: (a) a major amount of base stock selected from the group consisting of one or more Group IV oils, one or more Group V oils, mixtures of Group IV and Group V oils, and mixtures containing one or more Group III oils and at least one Group IV and/or Group V oils, the base stock having a NOACK volatility of 12% or less; (b) a calcium detergent; and (c) an organic friction modifier. The composition has a NOACK volatility of about 12 wt. % or less, contains from about 0.058 to 0.58 wt. % calcium from the calcium detergent, 0.02 to 2.0 wt. % of an oil soluble organic friction modifier and is free of any molybdenum additives. The composition may be prepared by the admixture of the ingredients and such compositions are a further embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Base Stock

[0007] The base stock of the invention consists essentially of one or more Group IV and/or Group V oils, a mixture of Group IV and Group V oils or a mixture consisting essentially of one or more Group III oils and one or more Group IV and/or Group V oils. The base stock used to prepare the lubricating oil composition of this invention a NOACK volatility of 12 wt. % or less, preferably 10 wt. % or less, more preferably 8 wt. % or less. Preferably the base stock(s) has a viscosity index of at least 120, preferably of at least 130, more preferably of at least 140. The base stock used to prepare the lubricating oil compositions of the present invention preferably has a kinematic viscosity of from about 3 to about 12 mm2/s at 100° C., preferably of from about 4 to about 10 mm/s at 100° C., most preferably of from about 5 to about 8 mm2/s at 100° C.

[0008] Examples of suitable base stocks may be found in one or more of the base stock groups, or mixtures of said base stock groups, set forth in the American Petroleum Institute (API) publication “Engine Oil Licensing and Certification System”, Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998.

[0009] a) Group I base stocks contain less than 90 percent saturates and/or greater than 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table A below.

[0010] b) Group II base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table A below.

[0011] c) Group III base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 120 using the test methods specified in Table A below.

[0012] d) Group IV base stocks are polyalphaolefins (PAO), a synthetic base stock.

[0013] e) Group V base stocks include all other base stocks not included in Groups I, II, III, or IV. 1 TABLE A Analytical Methods for Testing Base Stocks Property ASTM Test Method Saturates D200  Viscosity Index D2270 Sulfur D2622, D4292, D4927 or D3120 Napthenics (cycloparaffins) D3238 NOACK volatility D5800

[0014] When the base stock is a mixture of a Group III oil and one or more Group IV and/or Group V oil(s), at least 5%, preferably 30%, most preferably 60% of the total weight of base stock is a Group IV and/or Group V oil.

[0015] Calcium Detergent

[0016] The present invention requires the presence of at least one calcium detergent. Detergents aid in reducing deposits that build up in an engine and act as an acid neutralizer or rust inhibitor. This in turn reduces engine wear and corrosion. The use of a calcium detergent in combination with the base stocks in the composition of this invention offers fuel economy advantages as demonstrated by coefficient of friction data.

[0017] The calcium detergent used in this invention may be neutral or overbased and may comprise calcium phenates, salicylates, sulfonates, or mixtures thereof, with calcium sulfonates being particularly preferred. Preferably, the detergent will be overbased, that is the Total Base Number (TBN) will be at least 100 but usually between 100 and 500, more preferably between 150 and 450, and most preferably between 200 and 400. The most preferred detergent for use in this invention is an overbased calcium sulfonate having a TBN between 200 and 400.

[0018] The process of overbasing a metal detergent means that a stoichiometric excess of the metal is present over what is required to neutralized the anion of the salt. It is the excess metal from overbasing that has the effect of neutralizing acids that may build up in a lubricating oil, in use.

[0019] In the present invention, overbased calcium sulfonate detergents may be derived from the salt of an oil soluble sulfonic acid, where a mixture of an oil soluble sulfonate or alkaryl sulfonic acid is combined with calcium and heated to neutralize the sulfonic acid that is present. This forms a dispersed carbonate complex by reacting the excess calcium with carbon dioxide. The sulfonic acids typically are obtained by the sulfonation of alkyl substituted aromatic hydrocarbons such as those obtained from the fractionation of petroleum or by the alkylation of aromatic hydrocarbons. Examples include those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl or their halogen derivatives such as chlorobenzene, chlorotoluene, and chloronaphthalene. The alkylation may be carried out in the presence of a catalyst with alkylating agents having from 3 to more than 30 carbon atoms. For example, haloparaffins, olefins obtained by dehydrogenation of paraffins, or polyolefins produced from ethylene or propylene are all suitable. The alkaryl sulfonates usually contain from about 9 to about 70 or more carbon atoms, preferably from about 16 to about 50 carbon atoms per alkyl substituted aromatic moiety.

[0020] The oil soluble sulfonates are neutralized with a calcium compound. The amount of calcium that is used to neutralize the oil soluble sulfonate is carefully chosen with regard to the desired total base number (TBN) of the final product.

[0021] In the present invention, the amount of calcium detergents used can vary broadly, but typically will be from about 0.5 to about 5 wt. %, based on the total weight of the composition. This corresponds to about 0.058 to 0.58 wt. % calcium from the calcium detergent in the finished composition. Preferably the composition will contain between about 0.112 to 0.42 wt. % of calcium from the calcium detergent.

[0022] Calcium phenates and calcium salicylates may be prepared using a variety of methods well known in the art.

[0023] The calcium detergents of the present invention may be used in combination with other metal detergents, e.g., magnesium detergents, with the proviso that at least the minimum amount of calcium is provided to the lubricating oil, as described supra.

[0024] Friction Modifiers

[0025] At least one oil soluble organic friction modifier is incorporated in the lubricating oil composition in an amount of from about 0.02 to 2.0 wt. % of the lubricating oil composition. Preferably, from 0.05 to 1.0, more preferably from 0.1 to 0.5 wt. % of the friction modifier is used.

[0026] Friction modifiers include such compounds as aliphatic amines or ethoxylated aliphatic amines, aliphatic fatty acid amides, aliphatic carboxylic acids, aliphatic carboxylic esters of polyols such as glycerol esters of fatty acid as exemplified by glycerol oleate, aliphatic carboxylic ester-amides, aliphatic phosphonates, aliphatic phosphates, aliphatic thiophosphonates, aliphatic thiophosphates, etc., wherein the aliphatic group usually contains above about eight carbon atoms so as to render the compound suitably oil soluble. Also suitable are aliphatic substituted succinimides formed by reacting one or more aliphatic succinic acids or anhydrides with ammonia.

[0027] Representative examples of suitable friction modifiers are found in U.S. Pat. No. 3,933,659 which discloses fatty acid esters and amides; U.S. Pat. No. 4,105,571 which discloses glycerol esters of dimerized fatty acids; U.S. Pat. No. 3,779,928 which discloses alkane phosphonic acid salts; U.S. Pat. No. 3,778,375 which discloses reaction products of a phosphonate with an oleamide; U.S. Pat. No. 3,852,205 which discloses S-carboxyalkylene hydrocarbyl succinimide, S-carboxyalkylene hydrocarbyl succinimide acid and mixtures thereof; U.S. Pat. No. 3,879,306 which discloses N(hydroxyalkyl)alkenyl-succinimic acids or succinimides; U.S. Pat. No. 3,932,290 which discloses reaction products of di-(lower alkyl) phosphites and epoxides; and U.S. Pat. No. 4,028,258 which discloses the alkylene oxide adduct of phosphosulfurized N-(hydroxyalkyl)alkenyl succinimides. The disclosures of the above references are herein incorporated by reference. Examples of other friction modifiers are succinate esters, or metal salts thereof, of hydrocarbyl substituted succinic acids or anhydrides and thiobis-alkanols such as described in U.S. Pat. No. 4,344,853.

[0028] Examples of nitrogen containing friction modifiers, include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, amino guanadine, alkanolamides, and the like. Such friction modifiers can contain hydrocarbyl groups that can be selected from straight chain, branched chain or aromatic hydrocarbyl groups or admixtures thereof, and may be saturated or unsaturated. Hydrocarbyl groups are predominantly composed of carbon and hydrogen but may contain one or more hetero atoms such as sulfur or oxygen. Preferred hydrocarbyl groups range from 12 to 25 carbon atoms and may be saturated or unsaturated. More preferred are those with linear hydrocarbyl groups.

[0029] Other Components

[0030] Zinc dihydrocarbyldithiophosphate may be added to the lubricating oil composition. Preferably zinc dialkylthiophosphate (ZDDP) is used. This provides antioxidant and anti-wear properties to the lubricating composition. Such compounds may be prepared in accordance with known techniques by first forming a dithiophosphoric acid, usually by reaction of an alcohol or a phenol with P2S5 and then neutralizing the dithiophosphoric acid with a suitable zinc compound. Mixtures of alcohols may be used including mixtures of primary and secondary alcohols. Examples of such alcohols include, but are not restricted to the following list: iso-propanol, iso-octanol, 2-butanol, methyl isobutyl carbinol (4-methyl-1-pentane-2-ol), 1-pentanol, 2-methyl butanol, and 2-methyl-1-propanol. The zinc dihydrocarbyldithiophosphate compound can be a primary zinc, secondary zinc, or mixtures thereof, that is, the zinc compound contains primary and/or secondary alkyl groups derived from primary or secondary alcohols. The alkyl groups can have 1 to 25 carbons, preferably 3 to 12 carbons. Moreover, when employed, there is preferably at least about 50 wt. % secondary zinc from a dihydrocarbyldithiophosphate compound in the zinc dihydrocarbyldithiophosphate compound.

[0031] The lubricating oil composition preferably has a low phosphorus content, that is, the phosphorus from any zinc dihydrocarbyldithiophosphate present should be present in an amount up to about 0.1 wt. %. Preferably, the phosphorus content from the zinc dihydrocarbyldithiophosphate should be from about 0.025 wt. % to about 0.1 wt. %.

[0032] Particularly preferred are lubricating oil compositions which contain a ZDDP which is composed of at least 50 wt. % secondary zinc, preferably 75% or more secondary zinc, most preferably 85-100 wt. % secondary zinc, such as a ZDDP having 85% secondary alkyl groups and 15% primary alkyl groups such as a ZDDP made from 85% butan-2-ol and 15% iso-octanol. Amounts are present in the lubricating oil composition to preferably provide a phosphorus content (wt. % P) of up to about 0.1% and preferably 0.025-0.1 wt. % P in the finished oil composition. Such compositions allow for satisfactory results to be obtained in the Sequence IVA engine test for cam wear without the need for more expensive molybdenum containing additives.

[0033] The compositions can be used in the formulation of crankcase lubricating oils (i.e., passenger car motor oils, heavy duty diesel motor oils, and passenger car diesel oils) for spark-ignited and compression-ignited engines. The additives listed below are typically used in such amounts so as to provide their normal attendant functions. Typical amounts for individual components are also set forth below. All the values listed are stated as mass percent active ingredient. 2 MASS % MASS % ADDITIVE (Broad) (Preferred) Ashless Dispersant 0.1-20   1-10 Other Metal Detergents 0.1-15  0.2-9   Corrosion Inhibitor 0-5   0-1.5 Supplemental anti-oxidant 0-5 0.01-1.5  Pour Point Depressant 0.01-5   0.01-1.5  Anti-Foaming Agent 0-5 0.001-0.15  Supplemental Anti-wear Agents   0-0.5   0-0.2 Other Friction Modifiers 0-5   0-1.5 Viscosity Modifier 0.01-20    0-15 Synthetic and/or Mineral Base Stock Balance Balance

[0034] The ashless dispersant comprises an oil soluble polymeric hydrocarbon backbone having functional groups that are capable of associating with particles to be dispersed. Typically, the dispersants comprise amine, alcohol, amide, or ester polar moieties attached to the polymer backbone often via a bridging group. The ashless dispersant may be, for example, selected from oil soluble salts, esters, amino-esters, amides, imides, and oxazolines of long chain hydrocarbon substituted mono and dicarboxylic acids or their anhydrides; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having a polyamine attached directly thereto; and Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine.

[0035] Other metal-containing or ash-forming detergents, besides the calcium detergent, may be present and function both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with long hydrophobic tail, with the polar head comprising a metal salt of an acid organic compound. The salts may contain a substantially stoichiometric amount of the metal in which they are usually described as normal or neutral salts, and would typically have a total base number (TBN), as may be measured by ASTM D-2896 of from 0 to 80. It is possible to include large amounts of a metal base by reacting an excess of a metal compound such as an oxide or hydroxide with an acid such as carbon dioxide. The resulting overbased detergent comprises neutralized detergent as the outer layer of a metal base (e.g., carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically from 250 to 450 or more.

[0036] Such other known detergents include oil-soluble neutral and overbased, sulfonates, sulfonates, sulfurized phenates, thiophosphonates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e.g., sodium, potassium, lithium, and magnesium.

[0037] Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids may be used.

[0038] Copper and lead bearing corrosion inhibitors may be used, but are typically not required with the formulation of the present invention. Typically such compounds are the thiadiazole polysulfides containing from 5 to 50 carbon atoms, their derivatives and polymers thereof. Derivatives of 1,3,4 thiadiazoles such as those described in U.S. Pat. Nos. 2,719,125; 2,719,126; and 3,087,932; are typical. Other similar materials are described in U.S. Pat. Nos. 3,821,236; 3,904,537; 4,097,387; 4,107,059; 4,136,043; 4,188,299; and 4,193,882. Other additives are the thio and polythio sulfenamides of thiadiazoles such as those described in UK Patent Specification No. 1,560,830. Benzotriazole derivatives also fall within this class of additives. When these compounds are included in the lubricating composition, they are preferably present in an amount not exceeding 0.2 wt. % active ingredient.

[0039] Oxidation inhibitors or antioxidants reduce the tendency of base stocks to deteriorate in service which deterioration can be evidenced by the products of oxidation such as sludge and varnish-like deposits on the metal surfaces and by viscosity growth. Such oxidation inhibitors include hindered phenols, alkaline earth metal salts of alkylphenolthioesters having preferably C5 to C12 alkyl side chains, calcium nonylphenol sulfide, ashless oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons, alkyl substituted diphenylamine, alkyl substituted phenyl and naphthylamines, phosphorus esters, metal thiocarbamates, ashless thiocarbamates and oil soluble copper compounds as described in U.S. Pat. No. 4,867,890. Most preferred are the alkyl substituted diphenylamines.

[0040] Pour point depressants, otherwise known as lube oil flow improvers, lower the minimum temperature at which the fluid will flow or can be poured. Such additives are well known. Typical of those additives which improve the low temperature fluidity of the fluid are C8 to C18 dialkyl fumarate/vinyl acetate copolymers, polyalkylmethacrylates and the like.

[0041] Foam control can be provided by many compounds including an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.

[0042] A small amount of a demulsifying component may be used. A particularly suitable demulsifying component is described in EP 330,522. It is obtained by reacting an alkylene oxide with an adduct obtained by reacting a bis-epoxide with a polyhydric alcohol. The demulsifier should be used at a level not exceeding 0.1 mass % active ingredient. A treat rate of 0.001 to 0.05 mass % active ingredient is convenient.

[0043] The viscosity modifier (VM) functions to impart high and low temperature operability to a lubricating oil. Suitable viscosity modifiers are polyisobutylene, copolymers of ethylene and propylene and higher alpha-olefins, polymethacrylates, polyalkylmethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, inter polymers of styrene and acrylic esters, and partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadiene, as well as the partially hydrogenated homopolymers of butadiene and isoprene and isoprene/divinylbenzene. Multifunctional viscosity modifiers that also function as dispersants are also known and described, for example, in U.S. Pat. Nos. 4,092,255; 4,146,489; 5,663,126 and 6,187,721.

[0044] Some of the other above-mentioned additives can also provide a multiplicity of effects; thus for example, a single additive may act as a dispersant-oxidation inhibitor. This approach is well known and does not require further elaboration.

[0045] Preferably, the volatility of the lubricating oil composition, (as opposed to the base stock per se), measured using the NOACK Volatility Test, is about 12 wt. % or less, such as in the range of 2 to 12 wt. %, preferably in the range of 4 to 10 wt. %. The NOACK Volatility Test is used to measure the evaporative loss of the lubricating oil composition is the same as that used to measure the NOACK volatility of the base stock (according to the procedure of ASTM D5800). The wt. % reported represents evaporative loss.

[0046] The individual additives may be incorporated into a base stock in any convenient way. Thus, each of the components can be added directly to the base stock or base oil blend by dispersing or dissolving it in the base stock or base oil blend at the desired level of concentration. Such blending may occur at ambient temperature or at an elevated temperature.

[0047] Preferably, all the additives except for the viscosity modifier and the pour point depressant are blended into a concentrate or additive package described herein as the additive package, that is subsequently blended into base stock to make the finished lubricant. The concentrate will typically be formulated to contain the additive(s) in proper amounts to provide the desired concentration in the final formulation when the concentrate is combined with a predetermined amount of a base lubricant.

[0048] The final crankcase lubricating oil formulation may employ from 2 to 20 mass %, preferably 4 to 18 mass %, and most preferably about 5 to 17 mass % of additive with the remainder being base stock.

[0049] This invention also contemplates a method for improving the fuel economy and fuel economy retention properties of an internal combustion engine, which comprises the step of adding to the engine the lubricating oil composition of the present invention and operating the engine.

[0050] The invention is further illustrated by the following examples, which are not to be considered as limitative of its scope.

EXAMPLES

[0051] The Volkswagen T-4 test is part of the VW 503 00/506 00 specification for gasoline and turbo charged direct injection diesel engines and evaluates the extended drain characteristics of a lubricating oil. The parameters of the T-4 test are shown below: 3 Parameter VW T-4 Engine Type* 4 cylinder MPI Engine Disp. (cc) 1968  Test Duration (h) 248 Test Phases  4 Engine Speed (rpm)  820-4300 Air-to-Fuel Ratio (%) 0.5-4.1 Fuel Rate (kg/h)  1.1-19.4 Overall Load (N-m)   0-max Coolant Outlet  30-100 Temperature (° C.) Oil Temperature (° C.)  40-133 Fuel CEC RF 83 A-91 (ULG) Test Method PV 1449

[0052] An additive package was prepared containing dispersant, organic friction modifier, antioxidant, ZDDP antiwear agent, LOFI (lube oil flow improver) and calcium detergents in amounts providing the fully formulated oils with a calcium content of about 0.2 wt. %. The additive package, together with viscosity modifier was used to formulate lubricating oil compositions using base oil combinations as shown below.

[0053] The amount of added viscosity modifier was varied between the samples to provide a constant kinematic viscosity at 100° C. between the samples, such that all the samples met SAE viscosity requirements for 5W-40 viscosity grade. The difference in the amount of viscosity modifier was not believed to have influenced the test results. The additive package was provided as active ingredients in diluent oil that was not a Group III or higher oil. However, the amount of these lesser grade oils is considered de minimus relative to the amount of base stock. The number used to describe the poly-alpha olefin Group IV base stocks, as set forth below, refers to an average kinematic viscosity of the oil, expressed in cP. 4 Ex. 1 Ex. 2 (Comp.) (Inv.) VM 12.2 8.5 PAO 4 24.8 PAO 6 18.4 48.5 Group I 31.9 Group III 30.0 Adpac 12.7 13.0 100 100 Ca 0.198 0.198 NOACK 12.4 6.72 Grade 5W-40 5W-40

[0054] The oils had identical performance characteristics other than NOACK volatility. The base oil selection controls the NOACK volatility.

[0055] It was been found that the main parameter that fails in the Volkswagen T-4 is the % viscosity increase at 40° C. at the end of the test. Each test stand is calibrated with reference oil to determine the passing limits. The test data is summarized below: 5 Oil Code % Viscosity increase @ 40° C. Limit Ex. 1 158.8 (F) 133.14, max Ex. 2  29.8 (P)  135.8, max

[0056] The oil with the NOACK of 12.4 (Ex. 1) fails the test, whereas the oil with a NOACK of 6.72 (Ex. 2 of the invention) easily passes.

[0057] It should be noted that the lubricating oil compositions of this invention comprise defined, individual, i.e., separate, components that may or may not remain the same chemically before and after mixing. Thus, it will be understood that various components of the composition, essential as well as optional and customary, may react under the conditions of formulation, storage or use and that the invention also is directed to, and encompasses, the product obtainable, or obtained, as a result of any such reaction.

[0058] The disclosures of all patents, articles and other materials described herein are hereby incorporated, in their entirety, into this specification by reference. The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. What applicants submit is their invention, however, is not to be construed as limited to the particular embodiments disclosed, since the disclosed embodiments are regarded as illustrative rather than limiting. Changes may be made by those skilled in the art without departing from the spirit of the invention.

Claims

1. A lubricating oil composition for internal combustion engines which exhibits improved fuel economy and fuel economy retention properties, is free of molybdenum additives, has a NOACK volatility of 12 wt. % or less and which comprises:

(a) a major amount of base stock selected from the group consisting of one or more Group IV or Group V oils and mixtures thereof, and mixtures containing one or more Group III oils and at least one Group IV and/or Group V oils, the base stock having a NOACK volatility of 12% or less; and

(b) a calcium detergent present in such amounts so as to provide from about 0.058 to about 0.58 wt. % calcium in the composition; and

(c) from about 0.02 to about 2.0 wt. % of an oil soluble organic friction modifier.

2. The composition of claim 1, wherein the base stock comprises a poly-&agr;-olefin synthetic base stock.

3. The composition of claim 1, wherein said NOACK volatility of said base stock is 10% or less.

4. The composition of claim 1, wherein said NOACK volatility of said base stock is 8% or less.

5. The composition of claim 1, wherein the composition further comprises a zinc dialkyl dithiophosphate present in such amount to provide up to 0.1 wt. % phosphorus in the composition.

6. The composition of claim 5, wherein the zinc dialkyldithiophosphate has at least 50 wt. % secondary alkyl groups.

7. The composition of claim 1, wherein the calcium detergent is overbased.

8. The composition of claim 7, wherein the calcium detergent is a sulfonate.

9. The composition of claim 1, wherein the composition further comprises one or more of lubricating oil additives selected from the group consisting of ashless dispersants, other metal detergents, corrosion inhibitors, supplemental antioxidants, pour point depressants, anti-foaming agents, supplemental antiwear agents, other friction modifiers and viscosity modifiers present in such amounts so as to provide their normal attendant functions.

10. The composition of claim 1, wherein said base stock has a kinematic viscosity index of of from about 3 to about 12 mm2/s.

11. The composition of claim 10, wherein said base stock has a kinematic viscosity of from about 4 to about 10 mm2/s.

12. The composition of claim 1, wherein said base stock has a viscosity of at least 120.

13. The composition of claim 12, wherein said base stock has a viscosity of at least 130.