Development and Significance of the Phosphorus Emission Index of Engine Oils

This paper reports the author's effort to verify some of the present assumptions regarding causes and relationships in the volatility of engine oil phosphorus. Using Selby‐Noack volatility data from 1300 engine oils collected by the Institute of Materials in three areas of the world, volatilised phosphorus showed very low statistical dependence on either oil volatility or phosphorus concentration in the fresh oil. Rather, the data seemed to indicate that the chemistries of the phosphorus‐containing additives and their formulation with other additives were the controlling cause of phosphorus volatility and, by extension, emission level. The study permitted the development of a phosphorus emission index that predicts the emission potential of a formulated oil based on the amount of phosphorus found in the volatilised oil collected in the Selby‐Noack test.     

Analysis of engine oil and phosphorus volatility

An apparatus has been designed that allows the measurement of phosphorus volatility, which is important in, among other things, controlling the degradation of exhaust catalysers in automobiles. Following on from the original Noack volatility test, the Selby—Noack apparatus can measure up to 99.9% of volatiles. The apparatus has been used in the present work to assess the relationship between engine oil volatility and engine oil phosphorus volatility (from additives), some reflections on which are presented.     

Phosphorus volatility of engine oils: Use of the phosphorus emission index

The concept and principles of the phosphorus emission index (PEI) were introduced during 2002. This paper reviews the background of the benefits and concerns regarding phosphorus additives. In particular, the paper focuses on the two factors until recently assumed important in phosphorus volatility and catalyst contamination: oil volatility and initial phosphorus concentration. Studies of Selby—Noack data on 1300 oils collected in 1999 and 2000 by the Institute of Materials showed the invalidity of the two assumptions and this led to the concept of the PEl. Further studies in conjunction with a field taxi study by the Ford Motor Company to determine the correlation of the PEl with catalyst contamination not only showed correlation, but also proved that phosphorus volatility was independent of either oil volatility or fresh oil phosphorus levels. Rather, phosphorus volatility was, as earlier predicted, found to be highly dependent on its chemistry and the chemistry of other additives. Engine oil formulation using the PEl technique should markedly reduce phosphorus volatility and resultant catalyst contamination.     

A new approach to the Noack volatility test

This paper reports on the method and preliminary results of a significant modification of the Noack volatility test. This modification permits collection and examination of the volatile products as well as of the residue. The analysis of such volatiles by chromatography and spectroscopy revealed surprising information that is especially relevant in the face of increasingly difficult automotive and heavy duty engine emission limitations. The data also showed very close agreement with the Unified Test Method for the Noack Volatility Test now covered by CEC L-40-T-87. Important to operators, the authors' modified Noack apparatus avoids the use of the toxic Wood's Metal of the earlier Noack apparatus.     

Oxidation of mineral base oils of petroleum origin: The relationship between chemical composition,thickening, and composition of degradation products

The aim of this study was to improve understanding of high-temperature oxidation of base oils used in automobile engine oil formulations. Various oils were investigated: oils from the Middle East and the North Sea, with high and low aromatic and sulphur contents respectively; a hydro-isomerised polyalphaolefin oil with no aromatic or sulphur content; and a hydrocracked oil of intermediate composition. The influence of the aromatic and sulphur content and composition of the oils on thermo-oxidative degradation is investigated. These compounds give base oils natural protection from oxidation, but, under severe oxidation conditions, in the presence of a catalyst such as iron, which is always present in an engine, they become precursors of deposits. The action of two types of additive, radical inhibitors and hydroperoxide decomposers, was studied through oxygen consumption and thin-film oxidation tests. The oxidation products were identified; these provide insight into the degradation processes of the compounds during oxidation. They show too the influence of these processes on the formation of oxidised volatile species, on the increase in viscosity of the oil, and on the formation of oxidised species of high molar mass which, as they condense, contribute to the formation of insoluble compounds and deposits.     

The influence of engine oil on diesel exhaust emissions

Increasingly stringent emission legislation, together with the requirements for improved diesel engine performance, such as fuel economy, friction reduction, and extended drain intervals, have led to attention being focused on engine oil quality. The use of low‐friction engine oils can improve engine fuel efficiency and lead to a significant reduction of gaseous emissions. Therefore, engine oil is of importance when considering engine design parameters. This paper describes a study of the contribution of engine oil to diesel exhaust emissions. The investigations have shown that diesel engine particulate emissions as well as hydrocarbons and NO_X emissions depend on the lubricant oil properties, in particular on the sulphur content, volatility, and metal content.     

Development of a Methodology to Predict Cylinder Liner Scuffing in the 6V92TA Engine Lubricant Test©

The requirements placed on lubricating oils at the top ring reversal point are becoming increasingly severe due to recent changes in engine technology, most of which are driven by emissions regulations. As a result, revised engine tests to evaluate cylinder liner scuffing are being introduced to engine oil specifications. Despite the high cost and generally poor repeatability of full-scale engine data, no laboratory screener test is commercially available. In the present study, various lubricant characteristics were correlated with the level of scuffing in the Detroit Diesel 6V92TA engine test. Good initial agreement was obtained with lubricant volatility measured at 525°C, which is predicted to be the approximate contact temperature under the most extreme conditions likely to exist during normal operation.

Measurement of lubricant volatility, however, yields no indication of additive response and also appears to become less accurate when applied to unconventional basestocks. As a result, a laboratory-scale wear test was developed to predict scuffing resistance under high stress conditions. The results of the wear and volatility rests are combined using a simple equation to form the Diesel Engine Oil Scuff Test (DEOST). The resulting methodology provides an R² correlation of 70 percent with scuffing measured in the 6V92TA engine and is sensitive to both basestock characteristics and antiwear additives. In addition, the DEOST results indicated that viscosity index improvers provide little benefit under high-temperature operation, an effect commonly observed by failure of petroleum-based multigrade oils in the 6V92TA engine test.     

Composition and oxidative stability of hydro‐cracked base oils and comparison with a PAO

The oxidative stability of nine hydrocracked base oils from seven producers and a PAO was compared using the standard IP 48 test. After a comprehensive characterisation of the oils, an evaluation of oxidative stability was carried out by measuring some common oil parameters, such as viscosity characteristics, carbon residue, pentane insolubles, and acid number. Additionally, the compound‐class composition of the fresh and oxidised oils was determined, and an FTIR spectroscopic analysis was carried out. The oxidative stability of the hydrocracked oils was largely affected by the sulphur and aromatic hydrocarbon concentration in the oils. Oils with an increased sulphur content (above 80 ppm) had better oxidative stability than oils with a low sulphur content (20 ppm and lower), and there was a relatively large variability in the stability of the oils depending on the sulphur concentration. The oxidative stability of most of the hydrocracked oils with a low sulphur content was similar, and matched somewhat the stability of the polyalphaolefin.     

Evaluation of oxidation‐mediated volatility of hydrocarbon lubricant base fluids

Lubricant base fluids exhibit differences in volatility based on their molecular structures and the distribution of components. We report work to evaluate the volatilization of hydrocarbon base fluids using thermogravimetric analysis (TGA) and gas chromatographic simulated distillation. Commercial base fluids, including samples from API groups II, III, IV, have been evaluated. Kinematic viscosity was not a good predictor for volatility when all lubricants were considered. Polyalphaolefin (group IV) base fluids were found to have lower volatility than isoviscous group II and group III chemically modified mineral oil base fluids as measured by TGA, simulated distillation and Noack techniques. The advantages of TGA for measurement of lubricant volatility are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Lubricating oil additives and the environment — an overview

In this paper are reported some practical considerations relating to lubricant additive manufacture, and to additivated lubricants' impact on the environment. Widely used engine oil additives are mainly dithiophosphates, overbased calcium sulphonates, succinimidic dispersants, and polymer VI improvers. Production of these additives creates a potential environmental problems due to the hazardous emissions such as H₂S and HCl and sludge obtained during purification. New processes are described which lead to the reduction of toxic and other harmful pollutants. Gear oil additives, although these may be used in lower amounts, also make for ecological problems. A high quantity of sulphur-containing waste water is produced during manufacture of sulphurised EP additives. Some possibilities for recovering sulphur from this waste water are presented. The reduction of the chlorine content in EP additives is another important task, and new processes to produce EP additives with low residual chlorine content are discussed. Metal working fluid additives comprise emulsifiers, corrosion inhibitors, antiwear and EP additives. Their fabrication usually produces toxic and harmful residual products. Additivated lubricants may promote ecological injury. Oil leakage from engines working in harbours, parks, and entertainment areas are dangerous and difficult to avoid. To counter this, biodegradable base stocks were developed, but there are few data concerning the biode-gradability of the additives used. Used oils are generally collected and recovered, but a significant quantity of used oil is directly burned. Burning of additivated used oils in incorrect equipment leads to dangerous emissions, such as sulphur oxides. Because sulphur-containing additives cannot be replaced in engine oils or gear oils, the main ecological measure is the reduction of the quantity of used oils burned.     

Accumulation of lead in ester-based engine oils

Synthetic esters are widely used as base-oil components in top-tier crankcase lubricant formulations. In combination with synthetic hydrocarbons, an ester content of between 10 and 50 wt.% is common. Only a few engine oils with an ester content above 85 wt.% have been introduced on to the market as yet. The use of such engine oils is advantageous, especially in environmentally sensitive areas, in terms of volatility, particle emissions, and biodegradability. Some older types of heavy-duty diesel engine continue to be run in vehicles and in machinery in the construction industry, and in such engines a higher lead content has been detected when ester-based engine oils have been used. It has been found that lead is extracted from the bearings and accumulates ultimately in the engine oil during operation. Consequently, the development of a suitable inhibitor system has been initiated to improve engine and bearing protection. To determine the effectiveness of the new inhibitors, a suitable test method had to be found. Using a test method based on the Petter WI (CEC L-02-A-78) test engine, the present paper summarises the results of tests on an inhibitor system to prevent lead extraction from bearings The metal contents reported in this paper were determined by ion conductive plasma atomic emission spectrometry.     

Composition and oxidation stability of SAE 15W-40 engine oils

The modified IP 48 procedure was used for testing the oxidation stability of engine oils for ignition engines of the SAE 15W-40 and minimum API SG/CD specifications. Eight engine oils, such as Agip, BP, Esso, Mogul, ÖMV, Petro-Canada, Shell, and Total, were collected and oxidised. Oils were also fractionated by using chromatographic methods, and group composition of base oils, amount of VI improvers and other additives were determined. Several differences in the oxidation stability were found between the collected oils. Viscosity characteristics, carbon residue, acid number, amount of pentane insolubles and mass losses during the test were chosen as parameters for evaluation of the oxidation stability of the oils. The most stable engine oil was blended from a hydrocracked base oil whereas most of the other oils were based on the solvent refined oils.     

A method of measuring oil consumption by labelling with radioactive bromine

A method of determining the oil consumption rate of combustion engines is presented. It is based on labelling the individual oil fractions of engine oil with radioactive bromine isotope⁸² Br and on the quantitative absorption of radioactive bromine compounds in the exhaust gas in an aqueous solution of nitric acid and silver nitrate. The advantages of this method are that the oil that is consumed in the exhaust gas can be directly measured, without the fluctuating amounts of oil in the sump influencing the result, and the behaviour of the individual components of the oil in the consumption process can be determined. The test is quick, only twenty minutes being required to detect oil consumption at one operating point; and with a single labelling, the oil consumption at a great number of working engine points can be measured ⁸² Br has a short half‐life of only 36 h, so that compliance with radiation protection measures is inexpensive and investigations can be carried out using a conventional testing device. As part of the research project, a study was made of the influence of different base oil types, with and without polymer additives, on consumption. Results showed that Noack evaporation loss correlated with oil consumption only with boiling fractions of exactly the same base oil, and not with different, in particular synthetic, base oils; that polymer additives (VI improvers) significantly reduced the rate of oil consumption; and that the polymer additive and the type of base oil both had more influence on oil consumption than viscosity.     

Structure—activity correlations for sulphur EP additives

A series of new sulphur compounds was synthesised. Mercaptoheterocycles and mercaptoethanol were reacted with C₁₂-C₂₂ chloroacetates. Mercaptoethanol derivatives were subsequently reacted with trialkyl borates. The solubility of S-methylcarbalcoxy derivatives in both mineral oil and synthetic esters strongly depended on the alkyl group length, the most soluble being the C₁₂. C₁₄ derivatives. Three tests were used to estimate the antiwear (AW) and extreme pressure (EP) performance of the sulphur compounds: a four ball machine, an LFW-I machine, and a Falex tester. Despite some differences resulting from the test methods, the best EP characteristics were obtained with the 2-mercaptobenzothiazole derivatives. This showed that even a strongly bonded sulphur atom, such as that of the thiazolic ring, participates in surface layer formation. Mercaptoethanol derivatives were less soluble in either mineral or ester-based synthetic oils. Esterification of the hydroxyl groups with trialkyl borate improved their solubility and load carrying performance.     

Friction modifiers in engine and gear oils

Reducing friction is an important target for any lubricant oil formulator. There are several ways, such as utilisation of multi‐grade oils with low viscosity at low temperature, or use of friction modifiers, to reduce friction in automotive engines and transmissions and thus save fuel. A good means to obtain an energy‐saving lubricant is by the addition of a friction‐reducing additive in a high‐range multigrade oil. This paper presents some considerations on the action mechanism of friction modifiers and the results obtained in engine and gear oils with two new nitrogen‐, sulphur‐, and boron‐containing additives.     

Oil soluble polyethers in automotive crankcase lubricants

The evaluation of oil soluble polyethers (OSPs) in fully and semi-synthetic automotive crankcase lubricants is described. Parameters including viscosity, additive compatibility, lubricity/wear performance, oxidative stability, and piston cleanliness are assessed. It is possible to formulate OSP-containing lubricants with lower VI improver treatment level, superior viscometric properties, and Noack volatilities to comparable lubricants without OSPs. Data from engine tests and field trials show that semi- and fully synthetic lubricants containing OSP possess all the performance advantages of ester-containing lubricants, with additional benefits in terms of engine and inlet system cleanliness. The results indicate that OSPs have excellent potential as synthetic lubricant base fluids.     

Antifriction action of lubricant additives

The influence of antifriction additives for engine oils on fuel economy in gasoline engines has encouraged an interest in research into their action mechanisms. The influence of additives of different types on the antifriction properties of engine oils has now been investigated; additives have been discovered which effectively increase thermal stability of the lubricating layers and decrease friction coefficient, even at high temperatures. The structure and composition of the surface layers of friction pairs have been studied with Auger electron spectroscopy. The inter-relationship between the effectiveness of the antifriction action of the additives and their influence on the thickness and the composition of the surface layers has been ascertained. The most effective antifriction action was obtained where the thickness of the surface layers was reduced within certain limits, and where there was an optimisation of the oxygen and sulphur content. Certain regularities were established, since they were noticed while testing antioxidant, antiwear, antifriction, and detergent additives of different composition.     

Comparison of Antiwear Additive Response Among Several Base Oils of Different Polarities

The antiwear performance of tricresyl phosphate dissolved in 11 kinds of base oils of different polarities has been studied. A mineral oil (MO) and an alkylnaphthalene (AN) were used as non-or low-polarity base oils. Five polyol esters (POEs), i.e., three trimethylolpropane esters and two pentaerythritol esters, and four polyalkylene glycols (PAGs) were used as the high polarity base oils. A four-ball friction apparatus was used to determine the anti-wear performance, using commercially available bearing steel balls as test specimens. All the TCP-formulated base oils showed optimum concentration characteristics for minimizing wear. It is shown that the order of the optimum concentration for POEs and PAGs can be reasonably explained by the interaction between additive and base oils, by using their solubility parameters and molecular sizes. These oils' dielectric constants showed little correlation with optimum concentrations. The dielectric constant showed large effects on such non- or low-polarity oils as MO and AN. A good correlation of the optimum concentration for all the base oils was obtained when it was arranged as a function of (SP_base/SP_TCP)^14.2 (MW_base/MW_TCP)^?2.78 (ε)^18.6.     

Anti‐wear performance of organomolybdenum compounds as lubricant additives

A four‐ball tester was used to evaluate the anti‐wear performance of three kinds of organomolybdemun compounds in engine oils and lithium soap grease, i.e. molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate (MoDTC), and sulphur‐ and phosphorus‐free organomolybdeum (molybdate). The results indicate that a low concentration of MoDDP does not improve the anti‐wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti‐wear properties of the engine oils. MoDTC does not improve the anti‐wear properties of the engine oils, but worsens the anti‐wear properties of the oils. Significant improvement of the anti‐wear properties is obtained with molybdate added in the four fully formulated oils. Both MoDDP and molybdate have good anti‐wear properties in the lithium soap grease, especially MoDDP with a high concentration. Copyright © 2006 John Wiley & Sons, Ltd.     

The economic utilisation of sulphonation process residues in the petroleum industry

Sulphonation process residues in the petroleum industry are not exploited in line with their scientific or economic potential. The traditional routes for disposal of these residues can contribute to pollution, whereas various chemical techniques can be used to produce valuable products with domestic and industrial applications. The present work deals with the utilisation of sulphonation process residues. It is found that economic utilisation of sulphonation process residues from the petroleum industry involves the following:

• 1 A comparative evaluation of the performance of the products obtained with other available products demonstrated their efficiency and value.
• 2 Production of highly paraffinic oils with low aromatic content, with potential for use as spray oils, and the utilisation of their residues in the preparation of oil‐soluble neutral and overbased calcium sulphonates, to be used as detergentdispersant additives for crankcase lubricating oils.
• 3 Regeneration of used lubricating oils and use of their residues in the preparation of water‐soluble sodium sulphonates for use as surfactants.
• 4 Reducing the aromatic and sulphur content of kerosene for eventual employment as a carrier solvent for household in secticide.