AU717370B2 - Lubricating oil composition - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

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Name of Applicant: Address of Applicant: Actual Inventor: Pieter Jan Dirk MUNTZ XAM Corporation Pty Ltd 145 Main Street OSBORNE PARK WA 6017 Pieter Jan Dirk MUNTZ Address for Service: Wf-C Aasoo 4 =SCriffith Hack Co.

PO 90x &2qe2 256 A d elaide Terrac (6 Floor) EHo 2. PERTH WA 6000 v4A Gcoq- Standard Complete Specification for the invention entitled: LUBRICATING OIL COMPOSITION

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-0 22101(2) Details of Parent Application for Divisional Applications: Australian Complete Application No. 12045/92 The following is a full description of this invention, including the best method of performing it known to me:- (i I A i 1A LUBRICATING OIL COMPOSITION ag%" The present invention relates to lubricating oil 15 compositions, especially engine oils.

ot When two metal surfaces move over each other, considerable heat is evolved due to friction. The function of a lubricant is to separate the two rubbing surfaces by a film thereby greatly reducing the coefficient of friction.

If this film fails, the frictional heat produced may melt the surfaces causing them to weld together or seize. When conditions are such that a continuous thick (>0.001 in.) film of lubricant separates the solid surfaces at all points, then frictional resistance is controlled by the viscosity of the lubricant. This is referred to as "hydrodynamic lubrication". Under conditions of high speed or high load, thick lubricant films may be absent or incomplete and lubrication of the parts is effected by layers of adsorbed polar molecules. This situation is referred to as "boundary lubrication". Metal surfaces, which are covered by films of metal oxides, are highly polar and hence are not readily "wetted" by non polar hydrocarbon oils. Used alone, hydrocarbon oils are 2 therefore poor lubricants in these circumstances.

Lubricants therefore contain additives which either react with metal surfaces or are adsorbed on the surfaces thereby allowing oil to wet the surface or providing boundary lubrication, thus preventing direct metal to metal contact.

Apart from certain speciality products and synthetic oils, the vast bulk of lubricants are based upon hydrocarbons derived from petroleum.

Crude oils contain a number of broad classes of hydrocarbons, the proportions of which vary greatly from oil to oil.

Branched alkanes. These include iso- and anteiso alkanes, and linear derivates of isoprene such as phytane and pristane and degradation 15 products from molecules such as carotene. These compounds have low melting points and so confer low pour points on lubricating oils. They are also stable to degradation by heat and oxygen and have high viscosity indexes, so this iso-paraffin 20 group is the preferred feedstock for lube oil manufacture.

n-Alkanes. The paraffins have similar .properties to the iso-paraffins, except that, due to their higher melting points, they raise the pour point of a lube oil.

Cycloalkanes. The naphthenics contain fivemembered and six-membered rings with alkyl side chains. They lower the pour point of an oil but they have a low viscosity index.

Aromatics. These are derivatives of benzene, naphthalene and other fused ring systems with alkyl side chains. This group has a low viscosity index and poor thermal stability.

Sulphur compounds. This group forms a substantial proportion of many crudes, especially those from parts of the Middle East. It has similar properties to aromatics, but are usually even less stable.

3 In order to prepare a suitable lube oil base stock, a manufacturer will select feeds which have appropriate molecular weight ranges and are rich in the desired classes of hydrocarbons (iso-paraffins), and low in aromatics, ONS compounds, and paraffins so that production costs can be kept low. Crudes such as those from Pennyslvania which are ideal for lube oil manufacture are being depleted, so now most manufacturers use a feed stock mix which is carefully selected to meet the product mix required by the market. Some manufacturers upgrade their feedstock by using a severe hydrogenation/hydrogenolysis process called hydrocracking to remove sulphur, aromatics, and to open rings and crack larger molecules.

The residue from the primary distillation of 15 selected crude oils which are rich in iso-paraffins is distilled at reduced pressure (a few mm of Hg) in the presence of steam. Most usually, three fractions are obtained: two distillate cuts and the residue or bottoms.

Typical cuts are shown in the table below.

Lubricating Oil Fractions Fraction No. of C atoms Molecular Boiling Range °C Weight (Plant conditions) 9 Light 22-36 300-500 370-500 (Low viscosity) Medium 29-45 400-600 450-550 (medium viscosity) Heavy 43 600 >500(residue) (high viscosity) The desired oily alkane material is extracted from the viscous bottoms product from the vacuum tower using liquid propane (high pressure, 65 0 C) in a propane deasphalting plant. The more polar, high molecular weight polycyclic aromatics are less soluble in liquid propane than are the alkane (paraffin) components and are removed 4 as a hard sludge. Evaporation of the propane leaves the heaviest grade of lubricating oil which is usually referred to as "bright stock".

Each of the lube oil fractions is next treated with a solvent system which selectively removes much of the aromatic and 0, N, S material. Phenol and more recently furfural have been widely used in elaborate multistage counter current equipment for this purpose. The immiscible, slightly polar solvent selectively extracts the more polar aromatic material from the hydrocarbon mixture.

n-Alkanes (normal paraffins), which have higher melting points than branched alkanes of similar molecular weight, must be removed to decrease the low temperature viscosity of the lubricating oil. This is accomplished by S 15 taking the oil up in a suitable solvent such as a methylethylketone-toluene mixture and chilling 5-10 0 C below the required pour point. The n-alkanes are precipitated as "slack wax" which is separated by continuous filtration.

The final stage in manufacture of the base stocks 20 is hydrogenation to convert small amounts of dark-coloured unsaturated material into saturated material and to remove sulphur from sulphur compounds present in the oil.

Lubricating oils are finally prepared. by blending base stocks to give oil of the desired viscosity range, then introducing many additives to improve the life and performance of the oil.

The chemical composition of lubricating oils derived from crude oil is particularly complex. Normally lubricating oils contain a high proportion of naphthenic or paraffinic compounds. The hydrocarbons comprising a typical lubricating oil may have from 20 to 70 carbon atoms. Usually the hydrocarbons contained in lubricating oil have very few olefinic bonds. However there may be a significant proportion of hydrocarbons exhibiting aromatic unsaturation. A further description of base lubricating oils can be found in an article by D.V. Brock published in "Lubricant Engineering" Volume 43 pages 184-185 March 1987.

Minor improvements in the performance of a lubricating oil can yield significant economic benefits far in excess of the cost of the additive that provides the improved performance. The present invention is based on the discovery that the performance of lubricating oil compositions can be significantly improved by the addition of small amounts of a medium molecular weight paraffin to lubricating oil.

In accordance with the invention there is provided a lubricating oil composition comprising a base lubricating oil having typically between 20 and 70 carbon atoms, said lubricating oil composition characterised by having from between 0.1% and 2% by volume of an additive, wherein the additive comprises paraffins of medium molecular weight (MMWP) and having between 10 and 19 carbon atoms, so as to be effective in removing varnish and reducing the coefficient of friction between surfaces.

Preferably said additive is present in proportion from to 1.25% by volume.

The medium molecular weight paraffin (MMWP) may ooo comprise from 10 to 19 carbon atoms or from 10 to 17 carbon Gee.. 20 atoms but preferably it comprises from 10 to 15 carbon atoms. The composition may contain as little as 0.1% by volume of MMWP for an improvement in performance to be oo observed. Preferably however the engine oil composition of the present invention contains from 0.5% to 1% by volume of 25 a MMWP. Best results have been obtained with about 0.6% by oooo volume MMWP.

MMWP's are normally derived from the processing of crude oils. Normally they are produced during the initial o o atmospheric distillation of a crude oil and are gig characterised as hydrocarbons having a boiling point in the range from 150 to 335 0

C.

The compositions of the present invention may be prepared as compositions ready for use or as concentrates for premixing or mixing in situ e.g. in the sump of an engine. Concentrates may contain as much as 25% of the MMWP. The effective amount of MMWP required depends on the ultimate purpose of its inclusion and may also depend upon the additive selected.

6 A MMWP of particular interest is one known as "Shellsol Shellsol T is characterised as a solvent having the following properties-: Property Test Method Unit Specification Typical Value Distillation ASTM D1078 o

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Ranges, IBP 180 min 180.2 DP 205 max 202.5 Flash Point IP 170 oC 57.5 Aniline ASTM D611 o C 78-83 Point Density ASTM D1298 kg/ 0.765- 0.769 0 C litre 0.775 Composition %m Paraffins >99.8 Naphthenes <0.1 Aromatics <0.1 Other products of particular interest are those from the Shellsol series as well as Shell P874, Shell P878 and Ondina Oil 15. Shell P874 and P878 are technical white oils comprising a mixture of paraffins and naphthenes.

In an alternative and preferred embodiment, the additive is a technical white oil known as Shell P878, having a paraffins and naphthenes carbon percentage, according to the American Society for Testing Materials (ASTM) test method D2140 of approximately 58% and 42% 15 respectively. Preferably this technical white oil has a 'flash point of approximately 106 OC, an aniline point of approximately 82 and a density of approximately 0.807kg/litre.

In a further alternative and preferred embodiment, the additive is a technical white oil known as Shell P874 having a paraffins and naphthenic carbon percentage, according to the American Society for Testing Materials (ASTM) test method D2140 of approximately 79% and 21% respectively.

AL Preferably this technical white oil has a flash point of approximately 146 oC, an aniline point of approximately 6A- 97'C, and a density of approximately 0.799 kg/litre.

Paraffins of medium molecular weight include dodecane, hexadecane, octadecane and cosane.

The engine oil compositions preferred embodiments of the present invention are based on lubricating oil compositions that are normally commercially available.

These compositions may include various additives such as dispersants, detergents, oxidation inhibitors, foam inhibitors, pour point depressants and viscosity improvers.

A discussion of the function and formulation of lubricating oil compositions can be found in the "Handbook of Lubrication" Theory and Practice of Tribology Volume 1 edited by E. Richard Booser and published by CRC Press in 1983, the contents of which are incorporated herein by reference.

The composition of the present invention may also be incorporated into a grease composition with corresponding improvements in performance. Grease compositions normally comprise a metallic soap and a lubricating oil.

20 Similarly, the composition of the present invention may be used in other automotive applications.

Also in accordance with the invention there is provided a method of reducing varnishing and improving lubrication in mechanical systems selected from the group consisting of 25 internal combustion engines, gear boxes, and differentials, which method comprises the step of lubricating the engine, Sgear box, or differential with a lubricating oil composition as hereinbefore described.

:V Further in accordance with the invention there is provided a method of reducing varnishing and improving lubrication in mechanical systems selected from the group consisting of internal combustion engines, gear boxes, and differentials which method comprises the step of lubricating the engine, gear box, or differential with a lubricating oil composition comprising a base lubricating oil of relatively high molecular weight and having typically between about and 70 carbon atoms, said method comprising the step of 7 adding an additive to said lubricating oil composition in an amount of 0.1% to 2% by volume of said lubricating oil composition, said additive comprising paraffins of medium molecular weight and having between about 10 and 19 carbon atoms.

Preferably said paraffins have between 10 and 17 carbon atoms.

Preferably said paraffins have between 10 and 15 carbon atoms.

Preferably said additive comprises a paraffins carbon percentage of greater than 99.8%, a naphthenes carbon percentage of less than 0.1% and an aromatic carbon percentage of less than has a flash point of approximately 58 oC, an aniline point of approximately 80 oC, and a density of approximately 0.77 kg/litre.

Preferably said additive is a technical white oil also comprising naphthenes.

Preferably in said technical white oil, the paraffins and the naphthenes carbon percentage according to the American Society for Testing Materials (ASTM) test method D2140 is approximately 58% and 42% respectively Preferably said technical white oil has a flash point of approximately 106 an aniline point of approximately 87 and a density of approximately 0.807kg/litre.

25 Alternatively in the technical white oil, the paraffins and the naphthenic carbon percentage according to the American Society for Testing Materials (ASTM) test method D2140 is approximately 79% and 21% respectively.

Preferably said technical white oil has a flash point ooo 30 of approximately 146 an aniline point of approximately 97 oC, and a density of approximately 0.799 kg/litre.

The additive may be present in proportion from 0.5% to 1.25% by volume or preferably in proportion from 0.5% to 1% by volume. The most preferred amount of additive is present in proportion of about 0.6% by volume.

International Patent Application No. PCT/US89/05467 7A discloses lubricating oil compositions containing minute quantities of kerosene, the purpose of which is to carry silicone antifoam formulations into solution in a lubricating oil composition. However the quantities of medium molecular weight paraffins contained in the composition would be insufficient to be effective in the performance of the present invention. Normally the MMWP needs to comprise at least 0.1% to 0.5% by volume of the lubricating oil composition to be effective. Furthermore kerosenes frequently contain substantial proportions of aromatics which may negate the effect of the medium molecular weight paraffin.

The engine oils of the present invention provide a number of significant advantages over the existing formulations. These include the following: i. A noticeable reduction in varnishing; 2. A reduction in sludging; 3. Reduced production of harmful chemical by-products roe such as acids; oe 20 4. Improved seal life particularly seals in gearboxes, differentials and engines; 5. Reduced glazing especially when used in the preferred range; 6. Extended life of the engine oil; and 25 7. Reduced coefficient of friction of surfaces to o which it is applied.

The present invention also includes within its scope methods for any one or more of the following:

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a. reducing varnishing in an engine; 0 b. reducing sludging in an engine; c. reducing the production of harmful chemical by-products in an engine; d. improving seal life in an engine; and e. reducing glazing in an engine by incorporating an effective amount of a medium molecular weight paraffin into lubricating oil used in the engine.

4 Benefits provided by the present invention are illustrated by the accompanying comparative examples.

8 Example 1 The performance of the compositions of the present invention was compared with the performance of the compositions without the additive of the present invention using a pin on ball testing machine. The pin on ball testing machine comprises an electric motor driving a single shaft through a set of pulleys. A rotatable disc having a diameter of approximately 4cm is attached to the shaft and is rotated at a speed of 1200 1500 rpm. A separate shaft is pivoted at one end of the apparatus so that a hardened steel bearing element can be applied to the rotating disc. A torque wrench type configuration fitted to the pivoted shaft is used to determine the load applied to the rotating disc by the hardened steel bearing element.

15 Lubricant under test was applied to the bearing *"surface by splashing lubricant from a bath held at a base of the rotating disc. At all times during the test a continuous film of lubricant was in contact with the .bearing.

S 20 A series of seven oil samples was tested with the apparatus both with and without the addition of the "additive. Samples including the additive contained additive in the ratio of 1:80 additive to base lubricating oil composition.

25 The test procedure was as follows. With the disc rotating, a piece of coarse wet and dry emery paper was used to smooth any imperfections and score marks from the rotating disc prior to test. The bearing was moved to ensure a fresh unmarked surface was available for contact with the rotating disc. Prepared samples were poured into an oil bath containing approximately 20 to 40 mls and held in close contact at the base of the rotating disc which picked oil up and carried it across the bearing surface.

The bearing fixed to the pivoted shaft was lowered onto the rotating lubricated disc and allowed to settle in. A continuous load was manually applied to the handle of the pivoted shaft. The load was maintained and gradually increased until the bearing surfaces began to squeal. At the point when squealing commenced, the torque applied was 9 measured in ft.lb units. The results are set out in Table 1.

TABLE 1 RESULTS FOR OIL ADDITIVE ASSESSMENT

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a a, 'a i Applied Torque, ft.lb Sample Without Additive With Additive 1. Shell XMO 80-100 150-160 2. Shell Marine Oil 125 160 3. BP Engine Oil 80-110 140-150 4. BP Gear Oil 70 140 5. BP Grease 130 160 6. Caltex CXT 50 150 7. Esso Tiger 80 150 The additive used in this experiment was "Youngs 303" which is a lubricating oil used in cleaning guns. Gas chromatographic analysis of Youngs 303 revealed that it is a mixture of a lubricating oil and another hydrocarbon fraction of slightly higher boiling point than kerosene.

The kerosene like fraction had major components of carbon chain length 11 to 13. The kerdsene like fraction comprised approximately 50% of the "Youngs 303".

The results demonstrate that the oil additive provides enhanced performance under the harsh boundary lubrication conditions utilised.

Example 2 The performance of the lubricating oil compositions of the present invention were tested against a base lubricating oil composition in a V8 Caterpillar engine (Model 3408) of 450 horsepower. The results of the test are set out in Table 2. The additive used was Shellsol T in the ratio of 1:160 by volume.

10 TABLE 2 Test Results V8 CAT Engine b..

C.

.c Sb Test I Test II (with additive) Time Burn Horse R.P.M. Time Burn Horse R.P.M.

-Mins Rate/ Power -Mins Rate/ Power Hr Hr 5 61.7 221 2183 5 61.3 222 2184 61.7 221 2183 10 61.3 222 2184 10 15 61.7 221 2183 15 61.3 222 2184 61.7 221 2183 20 61.3 222 2184 The results of the test demonstrate that the lubricating oil composition of the present invention increases the power output of the motor and increases fuel efficiency.

Example 3 A test using a BP lubricating oil as a base was performed on a Holden V8 engine. The additive used was Shellsol T in the ratio 1:160. The results are illustrated in Table 3.

11 TABLE 3 Holden 253 V8 Using B.P. Oil.

WITHOUT ADDITIVE WITH ADDITIVE L/IDLE 650 775 775 H/IDLE H/P TORQUE 110 110 W/TEMP 85 95 OIL/TEMP S 10 OIL/PRESS 120 100 *oo E/VACUUM The dynamometer consistently indicated that the lubricating oil compositions of the present invention resulted in an idle speed that was consistently 125 rpm 15 greater than that for the base lubricating oil.

Example 4 The lubricating oil composition of the present invention was compared.with a -base lubricating oil over a range of engine speeds. The additive used was 9 20 Shellsol T in the ratio 1:160. The engine used was a Caterpillar (Model 3406) six cylinder 400 horsepower engine. The results of the test are shown in Tables 4 and Table 4 illustrates the performance of the engine using the base lubricating oil composition and Table illustrates the performance of the same engine using a lubricating oil composition of the present invention.

St. C 12 TABLE 4 Specifications Low Idle R.P.M.

High Idle R.P.M.

Full Load R.P.M.

Rack Setting Boost Pressure

B.S.F.C.

H.P. Setting Lube Oil Pressure Lube Oil Pressure 750 2280 2100 1.15 33 .357 347 at High Idle at Low Idle Test Figures Without Additive 758 2307 2100 RPM H.P. GPH BOOST EXHAU FUEL WATER OIL OIL FUEL -ST PRESS TEMP. TEMP. PRES RATIO TEMP.

2300 9 8 333 230 89.3 100.9 445 2200 223 26 365 220 88.9 100.9 420 *2100 315 45 401 220 89.7 100.3 415 2000 326 44 381 220 90.2 100.1 410 1900 322 43 377 220 90.1 100.1 405 1800 320 43 377 220 89.4 99.6 400 1700 315 41 385 220 89.6 98.6 400 1600 309 30 401 220 90.6 98.7 400 1500 297 27 423 220 90.6 99.2 400 1400 287 25 456 220 89.7 98.5 395 13 TABLE Specifications Low Idle R.P.M.

High Idle R.P.M.

Full Load R.P.M.

Rack Setting Boost Pressure

B.S.F.C.

H.P. Setting Lube Oil Pressure Lube Oil Pressure 750 2280 2100 Test Figures With Additive 772 2304 2100 0 S S

S.

High Idle Low Idle RPM H.P. GPH BOOST EXHAU FUEL WATER OIL OIL FUEL -ST PRESS TEMP. TEMP. PRES RATIO TEMP.

*2309 38 6 292 230 88.0 94.9 450 *2200 231 24 334 220 89.5 96.9 440 *2100 317 45 404 220 90.6 100.3 420 2000 326 44 398 220 90.0 99.5 410 1900 322 43 390 220 89.4 99.7 400 1800 320 41 386 220 89.9 99.8 400 *1700 318 40 394 220 88.9 98.7 400 *1600 310 30 410 220 89.5 98.9 400 *1500 299 26 440 220 88.7 98.2 400 1400 284 25 467 220 88.9 97.2 390 oI 'rI 14 The results illustrate that the lubricating oil composition of the present invention produces an increase in power output of 2 to 3 horsepower at low revs and at full load.

Example Engine Test illustrating anti-varnish benefits: When added to a 4 litre 6 cylinder engine, which had done over 130,000 kms, and which was beginning to "breathe" noticeably due to "varnishing", and after approximately 4,000 kms running with an oil change after 2,000 kms with additive, all "breathing" ceased, as observed with the naked eye. The additive used was Shell Sol T in the ratio of 1:160. Combustion was noticeably steadier and more even.

15 The same experiment was performed with another engine of similar age, and the same results were achieved.

Oil leaks from each of the motors were also reduced and in particular around the crankshaft protrusions.

20 With the additive included in further oil changes the result of "no breathing" was continued indefinitely, with the benefit of cleaner oil, next to no oil burning and better running.

Of course along with this other benefits were 25 observed such as improved fuel efficiency, increased engine performance and reduced engine wear.

performance and reduced engine wear.

Claims (5)

1. A lubricating oil composition comprising a base lubricating oil having typically between 20 and 70 carbon atoms, said lubricating oil composition characterised by having from between 0.1% and 2% by volume of an additive, wherein the additive comprises paraffins of medium molecular weight and having between 10 and 19 carbon atoms, so as to be effective in removing varnish and reducing the coefficient of friction between surfaces.

2. A lubricating oil composition according to claim i, characterised by the paraffins having between 10 and 17 carbon atoms.

3. A lubricating oil composition according to claim 2, characterised by the paraffins having between 10 and carbon atoms.

4. A lubricating oil composition according to any one of L. the preceding claims, characterised by the technical white eat. oil comprising a paraffins carbon percentage of greater than

99.8%, a naphthenes carbon percentage of less than 0.1% and 20 an aromatic carbon percentage of less than has a flash point of approximately 57.5 an aniline point of approximately 78 to 83 and a density of approximately 0.765 to 0.775 kg/litre. A lubricating oil composition according to any one of claims 1 to 3, characterised by the additive being a technical white oil also comprising naphthenes. @o 6. A lubricating oil composition according to claim characterised by the paraffins and the naphthenes carbon percentage of the technical white oil, according to the American Society for Testing Materials (ASTM) test method D2140 being approximately 58% and 42% respectively. 7. A lubricating oil composition according to claim 6, characterised in that the technical white oil has a flash RJ\ point of approximately 106 an aniline point of 16 approximately 87 0 C, and a density of approximately 0.807kg/litre. 8. A lubricating oil composition according to claim characterised by the paraffins and the naphthenic carbon percentage of the technical white oil, according to the American Society for Testing Materials (ASTM) test method D2140 being approximately 79% and 21% respectively. 9. A lubricating oil composition according to claim 8, characterised in that the technical white oil has a flash point of approximately 146 an aniline point of approximately 97 0 C, and a density of approximately 0.799 kg/litre. A lubricating oil composition as claimed in any one of the preceding claims characterised in that the additive is present in proportion from 0.5% to 1.25% by volume. 11. A lubricating oil composition as claimed in Claim characterised in that the additive is present in proportion "from 0.5% to 1% by volume. o o 12. A lubricating oil composition as claimed in Claim 11 characterised in that the additive is present in proportion of about 0.6% by volume. o oo o 13. A grease composition comprising a thickener and a lubricating oil composition as claimed in any one of the preceding claims. 14. A grease composition as claimed in claim 13 wherein said thickener comprises a metallic soap. A method of reducing varnishing and improving oo lubrication in mechanical systems selected from the group consisting of internal combustion engines, gear boxes, and differentials, which method comprises the step of lubricating the engine, gear box, or differential with a lubricating oil composition as claimed in any one of claims 1 to 12. 16. A method of reducing varnishing and improving 1 17 lubrication in mechanical systems selected from the group consisting of internal combustion engines, gear boxes, and differentials which method comprises the step of lubricating the engine, gear box, or differential with a lubricating oil composition comprising a base lubricating oil of relatively high molecular weight and having typically between 20 and carbon atoms, said method comprising the step of adding an additive to said lubricating oil composition in an amount of 0.1% to 2% by volume of said lubricating oil composition, said additive comprising paraffins of medium molecular weight and having between 10 and 19 carbon atoms. 17. A method according to claim 16, characterised by the paraffins having between 10 and 17 carbon atoms. 18. A method according to claim 17, characterised by the paraffins having between 10 and 15 carbon atoms. 19. A method according to any one of claims 16 to 18, characterised in that the additive comprises a paraffins carbon percentage of greater than 99.8%, a naphthenes carbon percentage of less than 0.1% and an aromatic carbon 20 percentage of less than has a flash point of approximately 58 0C, an aniline point of approximately 80 0C, and a density of approximately 0.77 kg/litre. A method according to any one of claims 16 to 18, characterised in that the additive is a technical white oil also comprising naphthenes. 21. A method according to claim 20, characterised in that in the technical white oil, the paraffins and the naphthenes ooo carbon percentage according to the American Society for Testing Materials (ASTM) test method D2140 is approximately o 30 58% and 412% respectively 22. A method according to claim 21, characterised by the technical white oil having a flash point of approximately 106 OC, an aniline point of approximately 87 0C, and a density of approximately 0.807kg/litre. -a 3 23. A method according to claim 20, characterised in that 18 in the technical white oil, the paraffins and the naphthenic carbon percentage according to the American Society for Testing Materials (ASTM) test method D2140 is approximately 79% and 21% respectively. 24. A method according to claim 23, characterised by the technical white oil having a flash point of approximately 146 an aniline point of approximately 97 and a density of approximately 0.799 kg/litre. A method as claimed in any one of claims 16 to 24 characterised in that the additive is present in proportion from 0.5% to 1.25% by volume. 26. A method as claimed in Claim 25 characterised in that the additive is present in proportion from 0.5% to 1% by volume. 27. A method as claimed in Claim 26 characterised in that the additive is present in proportion of about 0.6% by volume. 28. A lubricating oil composition substantially as herein described with reference to the description of the embodiment. A method of reducing varnishing and improving lubrication in mechanical systems substantially as herein described with reference to the description of the to o oo.o embodiment. DATED this Seventh day of January 2000 0 PIETER JAN DIRK MUNTZ Applicant Wray Associates Perth, Western Australia Patent Attorneys for the Applicant(s)