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The earlier editions of this title have been best-selling definitive references for those needing technical information about automotive fuels. This long-awaited latest edition has been thoroughly revised and updated, yet retains the original fundamental fuels information that readers find so useful. This book is written for those with an interest in or a need to understand automotive fuels. Because automotive fuels can no longer be developed in isolation from the engines that will convert the fuel into the power necessary to drive our automobiles, knowledge of automotive fuels will also be essential to those working with automotive engines. Small quantities of fuel additives increasingly play an important role in bridging the gap that often exists between fuel that can easily be produced and fuel that is needed by the ever-more sophisticated automotive engine.

Developed by Rudolph Diesel in the 1890s, the diesel powertrain is used in many applications worldwide. For significant time the engine fuel source for these engines was petroleum diesel, until new legislation regarding emission reduction and smog mitigation saw the introduction of petroleum diesel and biodiesel (Fatty acid methyl ester; FAME) blends in the early 2000s. Since then there have been many instances of filters in diesel powertrains across heavy, light and off-road platforms becoming blocked with unidentified material, for example in the United States, Northern Europe and Scandinavia. Filters are designed to remove contaminants from the fuel system and as the filter becomes plugged it restricts the fuel flow resulting in loss of engine power and eventual breakdown. Understanding The nature of the material responsible for such blockages is clearly important to the industry and has been the subject of many studies.

The increased severity and prevalence of insoluble deposits formed on fuel injectors in gasoline direct injection (GDI) engines precipitates negative environmental, economic and healthcare impacts. A necessary step in mitigating deposits is to unravel the molecular compositions of these complex layered materials. But very little molecular data has been acquired. Mass spectrometry shows promise but most techniques require the use of solvents, making them unsuited for analyzing insoluble deposits. Here, we apply the high mass-resolving power and in-situ analysis capabilities of 3D OrbitrapTM secondary ion mass spectrometry (3D OrbiSIMS) to characterize deposits formed on the external tip and internal needle from a GDI injector. This is the first application of the technique to study internal GDI deposits. Polycyclic aromatic hydrocarbons (PAHs) are present up to higher maximum masses in the external deposit.

Over the last decade, there has been an impetus in the automobile industry to develop new diesel injector systems, driven by a desire to reduce fuel consumption and proscribed by the requirement to fulfil legislation emissions. The modern common-rail diesel injector system has been developed by the industry to fulfil these aspirations, designed with ever-higher tolerances and pressures, which have led to concomitant increases in fuel temperatures after compression with reports of fuel temperatures of ~150°C at 1500-2500 bar. This engineering solution in combination with the introduction of Ultra Low Sulphur diesel fuel (ULSD) has been found to be highly sensitive to deposit formation both external injector deposits (EDID) and internal (IDID). The deposits have caused concerns for customers with poor spray patterns misfiring injector malfunction and failure, producing increased fuel consumption and emissions.

The impact of internal diesel injector deposits (IDIDs) on engine performance, efficiency and emissions remains a major concern in the automotive industry. This has been compounded in recent years by fuel injection equipment developments and changes to diesel fuel towards ultra-low sulfur diesel (ULSD) and biodiesel as well as the introduction of new fuels such as hydrotreated vegetable oil (HVO). Prevention and mitigation of such deposit formation requires an understanding of the formation process, which demands a chemical explanation. The chemistry of these deposits therefore remains a key research interest to the industry using the latest analytical methodologies to inform and build further on previous investigations.

Studies of diesel system deposits continue to be the subject of interest and publications worldwide. The introduction of high pressure common rail systems resulting in high fuel temperatures in the system with the concomitant use of fuels of varying solubilizing ability (e.g. ULSD and FAME blends) have seen deposits formed at the tip of the injector and on various internal injector components. Though deposit control additives (DCAs) have been successfully deployed to mitigate the deposit formation, work is still required to understand the nature and composition of these deposits. The study of both tip and internal diesel injector deposits (IDID) has seen the development of a number of bench techniques in an attempt to mimic field injector deposits in the laboratory. One of the most used of these is the Jet Fuel Thermal Oxidation Tester or JFTOT (ASTM D3241).

The effect of legislation in driving towards lower emissions has seen significant changes in injector design, (common- rail) and fuel composition (ULSD). This has led to numerous reports of deposits throughout the vehicle diesel system, filters, tanks, pumps and injectors. In recent examples, deposits internal to the fuel injector on the needle have become prevalent and characterisation of the deposits on the injector needle has become an industry priority. A number of studies have made progress on this but the deposits have proven difficult to fully characterise and often have an ineradicable nature, which makes analysis other than in situ difficult. This paper will describe for the first time the application of a number of surface techniques, in combination which not only provide characterisation data but also the ability to provide cross-sectional lifts out of the sample, which may then be the subject of further analysis.

Since 2009, there has been a rise in deposits of various types found in diesel fuel injection systems. They have been identified in the filter, the injector tip and recently inside the injector. The latter internal diesel injector deposits (IDIDs) have been the subject of a number of recent publications, and are the subject of investigations by CRC (Central Research Council Diesel Performance Group-Deposit Panel Bench/ Rig Investigation sub panel) in the US and CEN (Committee European de Normalisation TC19/WG24 Injector Deposit Task Force) and CEC (Coordinating European Council TDFG-110 engine test) in Europe. In the literature one of the internal injector deposit types, amide lacquers, has been associated with a poorly characterised noncommercial low molecular weight polyisobutylene succinimide detergent which also lacked provenance.

There have been reports of internal injector deposits causing problems in diesel engines in the field from 2008. Such problems manifest themselves as rough idling, power loss, high emissions, high-pressure fuel pump wear, injector sticking, internal component corrosion and engine failure. These reports coincided with the use of common rail diesel injection systems and of ultra-low sulphur fuels introduced because of emission regulation demands. The injection systems have design features that are more conducive or susceptible to deposit formation such as severe high temperature and pressure operating conditions, the tolerances of critical parts, and lower force internal component actuation. The changes to fuels have also affected the fuels ability to solubilise these deposits. The deposits formed manifest themselves in complex form in the field, often being mixtures of inorganic and organic compounds.

The nature of internal diesel injector deposits (IDID) continues to be of importance to the industry, with field problems such as injector sticking, loss of power, increased emissions and fuel consumption being found. The deposits have their origins in the changes in emission regulations that have seen increasingly severe conditions experienced by fuels because of high temperatures and high pressures of modern common rail systems and the introduction of low sulphur fuels. Furthermore, the effect of these deposits is amplified by the tight engineering tolerances of the moving parts of such systems. The nature and thus understanding of such deposits is necessary to both minimising their formation and the development of effective diesel deposit control additives (DCA).

Deposit control additives have been added to diesel fuel for over 30 years to prevent the build-up of deposits in the fuel injection system and thereby ensure optimum engine operation. As the complexity of modern diesel fuel injection systems has increased their tolerance to deposit formation has decreased and therefore there is now an even greater need for high quality deposit control additives. The predominant and most effective chemistry for diesel deposit control additives used over the past 30 years is polyisobutylene succinimides (PIBSI). The design and manufacture of these additives is critical to their performance in the field in terms of functioning to control deposits but also from a no-harm standpoint. Recent work has identified low molecular weight PIBSI as a cause of internal diesel injector deposits (IDID) associated with injector sticking.

Diesel fuel distilled from crude oil should contain no greater than trace amounts of sodium. However, fuel specifications do not include sodium; there is a limit of five parts per million for the amount of sodium plus potassium in fatty acid methyl esters (FAME) used as biodiesel. Sodium compounds are often used as the catalyst for the esterification process for producing FAME and sodium hydroxide is now commonly used in the refining process to produce ultra-low sulphur diesel (ULSD) fuel from crude oil. Good housekeeping should ensure that sodium is not present in the finished fuel. A finished fuel should not only be free of sodium but should also contain a diesel fuel additive package to ensures the fuel meets the quality standards introduced to provide reliable operation, along with the longevity of the fuel supply infrastructure and the diesel engines that ultimately burn this fuel.

The recent developments in diesel fuel injection equipment coupled with the moves in the US to using ULSD and biodiesel blends has seen an increase in the number of reports from both engine manufacturers and fleet operators regarding fuel system deposit formation issues. These deposits not only form on and within the fuel injectors but they also form elsewhere in the fuel system, due to fuel recirculation. These will eventually accumulate in the fuel filters. Historically, diesel fuel system deposits have been attributed to contamination of the fuel or the degradation of the fuel with age. Such age related degradation has been attributed to oxidation of the fuel via well documented pathways, although the initiation of this process is still poorly understood. Papers at recent SAE meetings in Florence, San Antonio, Rio de Janeiro, San Diego and Kyoto have addressed many of these causes.

Traditionally, diesel fuel injection equipment (FIE) has frequently relied on the diesel fuel to lubricate the moving parts. When ultra low sulphur diesel fuel was first introduced into some European markets in the early 1980's it rapidly became apparent that the process of removing the sulphur also removed other components that had bestowed the lubricating properties of the diesel fuel. Diesel fuel pump failures became prevalent. The fuel additive industry responded quickly and diesel fuel lubricity additives were introduced to the market. The fuel, additive and FIE industries expended much time and effort to develop test methods and standards to try and ensure this problem was not repeated. Despite this, there have recently been reports of fuel reaching the end user with lubricating performance below the accepted standards.

The need to meet the US 2007 emissions legislation has necessitated a change in Diesel engine technology, particularly to the fuel injection equipment (FIE). At the same time as these engine technology changes, legislation has dictated a reduction in fuel sulphur levels and there has also been increased use of fatty acid methyl esters (FAME) or biodiesel as a fuel blending component. The combination of changes to the engine and the fuel has apparently led to a sharp rise in the number of reports of field problems resulting from deposits within the FIE. The problem is usually manifested as a significant loss of power or the engine failing to start. These symptoms are often due to deposits to be found within the fuel injectors or to severe fouling of the fuel filter. The characteristics of the deposits found within different parts of the fuel system can be noticeably different.

The fuel injection equipment (FIE) has always been paramount to the performance of the Diesel engine. Increasingly stringent emissions regulations have dictated that the FIE becomes more precise and sophisticated. The latest generation FIE is therefore less tolerant to deposit formation than its less finely engineered predecessors. However, the latest emissions regulations make it increasingly difficult for engine manufacturers to comply without the use of exhaust aftertreatment. This aftertreatment often relies on catalytic processes that can be impaired by non-CHON (carbon, hydrogen, oxygen and nitrogen) components within the fuel. Fuel producers have therefore also been obliged to make major changes to try and ensure that with the latest technology engines and aftertreatment systems the fuel is still fit for purpose. However, there has recently been a significant increase in the incidence of reported problems due to deposit build-up within vehicle fuel systems.

Recent developments in diesel fuel injection equipment coupled with moves to using ULSD and biodiesel blends has seen an increase in the number of reports, from both engine manufacturers and fleet operators, regarding fuel system deposit issues. Preliminary work performed to characterise these deposits showed them to be complicated mixtures, predominantly carbon like but also containing other possible carbon precursor materials. This paper describes the application of the combination of hydropyrolysis, gas chromatography and mass spectrometry to the analysis of these deposits. It also discusses the insights that such analysis can bring to the constitution and origin of these deposits.

Recent developments in diesel engines and fuel injection equipment together with the move to ULSD and bio-blends have seen an increase in reports regarding deposits in both injectors and filters. Historically deposits have been generated from a number of sources: bio-contamination, both aerobic and non-aerobic, water contamination, lube oil adulteration, additives, dirt, metals in fuel, and biodiesel degradation. These may be ascribed to “poor housekeeping,” incorrect additivation, deliberate adulteration or some combination. However the recently observed deposits differ from these. The deposits are described and indicate possible precursor molecules that support proposed mechanisms and their ability to form filter deposits.