Volatility, engine oil

D 5480 D 5533 Engine Oil Volatility by Gas Chromatography Evaluation of Automotive Engine Oils in the Sequence HIE Spark Ignition Engine... 

There is currently a shift to oils of lower viscosity that reduce engine friction and thereby improve fuel economy. These oils will be in increasing demand by automakers to meet government-mandated minimum miles-per-gallon requirements. A second change is a reduction in oil volatility, which reduces oil consumption and evaporative emissions into the environment. A strong dependence of diesel particulate emissions on engine oil volatility has been shown [25]. 

A test is also available for the determination of engine oil volatility at 371°C (700°F), which is actually a requirement in some lubricant specihca-tions (ASTM D-6417). This test method can be used on lubricant products not within the scope of other test methods with simulated distillation methodologies (ASTM D-2887). Applicabihty of this test method is hmited to samples with an initial boihng point higher than 126°C. This test method may be apphed to both lubricant oil base stocks and hnished lubricants containing additive packages. 

Association of Phosphorus Emission with Oil Consumption and Volatility—Oil consumption caused by oil volatility has always been a concern for automotive engineers because of the associated deposits often formed on piston rings, combustion chambers, and valves. Concern that oil volatility could cause phosphorus in the exhaust stream adds to the desire to reduce oil volatility. Consequently, progressively lower formulated engine oil volatility (as measured by the classic Noack volatility test [9-12]) was required for oils meeting API and ILSAC GF-2 (22 % loss) and GF-3 (15 % loss) specifications. 

A study of data published by the Institute of Materials (lOM) [18] for the years 1999 and 2000 of over 1200 oils was used. Phosphorus volatilized from fresh engine oils was ccm rared to 1) dieir oil volatilities and 2) initial phosphorus concentrations. Phosjdiorus volatility was first shown not to be dependent on engine oil volatility, as can be seen in Fig. 3 wdiere phosphoms volatility varies independently of the associated engine oil volatility. 

FIG. 3—Showing lack of relationship between the grams of an engine oil volatilized in the special Noack test (from an initial charge of 65 g for the test) and the grams of phosphorus volatilized during the same test. 

Selby, T. W. and Reichenbach, E. A., Engine Oil Volatility Studies - Generation of Phosphorus, Proceedings of the International Tribology Conference, Yokohama, Japan, 1995, pp. 813-816. 

In 2002, a paper was published on the phosphorus volatility results that appeared in the lOM database from 1999-2001 [9]. Contrary to expectations, it was found that phosphorus volatility was neither related to engine oil volatility nor to the phosphorus content in the unused engine oil. It was speculated that this lack of correlation with initial phosphorus additive concentration could be explained by either or both 1) effects of other engine oil additives and 2) variations in the chemistry of the phosphorus additives. A 2002 field study conducted by Ford Motor Company of catalyst degradahon by phosphorus-containing oils [10] was subsequently shown to correlate with the PEI data generated from the Selby-Noack bench test and, further, showed that phosphorus volatilization was strongly affected by other oil additives [11]. 

There are five types of reservoir fluids. These are usually called black oil, volatile oil, retrograde gas, wet gas, and dry gas. The five types of reservoir fluids have been defined because each requires different approaches by reservoir engineers and production engineers. 

Preparation. In the laboratory prepn of Compo-sition C-4, dry RDX is added to a petroleum ether soln of di(2-ethylhexyl)sebacate, polyisobutylene SAE 10 engine oil. The solvent is evaporated and the residue worked by hand into a homogenous dough-like mass. Since the use of a volatile flammable solv is undesirable in plant production, a solventless process was developed. In the plant process two different granulations of RDX are used 61 parts of Class (or Class B) 30 parts of Class 3 (See description of RDX classes under Cyclo-trimechylenetrinitramine in this vol of Encyclopedia). The water-wet mixture of both is placed in a stainless steel mixing kettle and 9 parts of "polyisobutylene" binder are added. 

Use a lower viscosity grade oil to reduce fluid friction under high speed driving conditions at low temperatures. Low-viscosity and low-volatility base oils, such as poly-a-olefin PAO or hydrorefined base oils, are necessary for the next generation of fuel-saving engine oils, such as those required to meet specification... 

It should also be mentioned that low oil viscosity at low temperatures is desirable in the new small 4 cylinder and V-6 cylinder fuel economy automobiles ( 5, 6). This is to permit sufficient speed of engine cranking for cold weather starting at winter temperatures. Low oil volatility must be maintained to prevent oil misting and blowby from poisoning the catalyst system and oxygen sensors in the anti-pollution devices (7). 

Compared on an equal viscosity basis, the properties of a polybutene, a PAO and an ester, the polybutene is more volatile, less resistant to oxidation and has a lower viscosity index. This illustrates the limitations of polybutene as a true synthetic base oil. For example, it would be inappropriate to use a low-viscosity polybutene as the base oil for crankcase engine oils. Polybutenes are used as a major base fluid for... 

In addition to lower volatility requirements, modern engine oils formulated after 2004 are subject to elemental limitations on sulphur content for improved emission system compatibility. Table 4.12. These restrichons on sulphur content have essentially eliminated the use of Group I base oils in modern engine oil formulation and thereby have contributed to a great improvement in oxidahve stability of modern engine oils. 

Data have been reported showing HSD VI improvers are reported to contribute less viscosity to the CCS than PMA or OCP, permitting the use of a heavier base stock [82], which had a favourable effect on base oil volatility reflected in improved oil consumption. Several reports demonstrated that dispersant PMA or OCP VI improvers in some cases permit a significant reduction in ashless dispersant level for fully formulated engine oils, also permitting use of a heavier base stock [17, 83]. 

Used engine oils can be reused. Sometimes, all that is needed is removal of particles by filtration or centrifugation. In others, it may be necessary to remove volatile acids and water by heating, followed by treatment with sulfuric acid, then lime, and, sometimes, bleaching clay. A final distillation under vacuum completes the rerefining.63 Another system uses propane at ambient temperature in a continuous process.64 The additives and impurities precipitate and settle out, after which the propane is flashed off and the... 

In a pair of papers, Selby et al. (Savant, Inc. and Astaris LLC) describe using phosphorus as an indicator of volatility of engine oils. Phosphorus is volatilized during Noack volatility test (ASTM D 5800). The volatile material is trapped and analyzed for total phosphorus using ICP-AES, and for phosphorus species using P NMR spectroscopy. 

Phosphorus Concentration Reduction and Concerns— A more challenging and debated direction in limiting phosphorus volatility was to limit the concentration of ZDDPs in engine oil. Understandably, this brought intense discussion among automotive and lubrication engineers reagarding ... 

Volatility of Fresh Engine Oils Compared to Their Phosphorus Volatility... 

FIG. 4—Showing lack of relationship between the concentration of phosphorus in a fresh engine oil and the concentration of phosphorus volatilized from the particular engine oil in the special Noack test. 

Considering die lack of relationship of volatilized phosphorus with eiflier oil volatility or initial phosphorus concentration in the oil, it seemed important to have a measure of the comparative phosphorus volatility of engine oils. This led to a concept of ranking engine oils based on the volatility of their phosphorus-containing additive(s) [20]. The ranking method was called the Phosphorus Emission Index, or PEI. 

Further work testing the significance of the PEI concept was undertaken as a consequence of taxi fleet tests of phosphorus volatility and catalyst degradation conducted by Ford Motor Company [22,23]. Interest in fhe PEI concept led Ford engineers to submit three blind-coded, fresh engine oils of the several fhat had been used in die taxi fleet tests. 

Thus, the PEI analysis of the Ford Motor Company field study resolved the previous posed question [20] of whether other additives in the oil formulation can influence the volatility of phosphorus. More specifically and importantly, it seems apparent that engine oil formulation can be tailored to control phosphorus volatility. 

PEIs of the Comparator and Reference Otis—Volatilities and PEIs using die special Noack were obtained on fiiese two oils, and results are shown in Table 2. As expected, the formulation wifiiout ZDDP, RO 779, shows no phosphorus in eiflier file formulation or the volatiles. In comparison, RO 780 has a PEI of 4.0 — considered relatively low among the engine oils collected aroimd the world for the international engine oil database of the lOM. 

For piurposes of determining the effect of large differences in PEI on the NMR signature of the volatile and residual material, four oils having similar oil volatilities but widely different phosphorus volatilities were requested from the North American lOM engine oil database. These samples were kindly supplied, and results are shown in Table 3 and Fig. 7 (also including RO 780 for comparison). 

Compart to phosphorus concentrations of the fresh engine oils. Table 3 and Fig. 7 show that the volatilized material of file four oils has widely different concentrations of phosphorus and, thus, considerably different levels of associated PEIs. It was considered reasonable that these oils would provide good opportunity in later NMR studies [24] to determine fire cause(s) of differences in phosphoras volatility and the related PEI. 

TABLE 3—Comparative oil and phosphorus volatilities of four marketed engine oils of considerably different PEIs. 

Table 3 - Volatilities and PEIs of Four Marketed Engine Oils North American Sector of the lOM Enolne Oil Database ...

FIG. 7—Variation cf PEI among four marketed North American engine oils of different formulations with somewhat similar overall volatility loss and initial phosphorus concentrations. 

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