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The demonstration benefit from fuel-borne fuel-economy additives to a precision of 1%, or better, traditionally requires very careful experimental design and considerable resource intensity. In practice, the process usually requires the use of well-defined drive cycles (e.g. emission certification cycles HFET, NEDC) in conjunction with environmentally-controlled chassis dynamometer facilities. Against this background, a method has been developed to achieve high-precision fuel economy comparison of gasoline fuels with reduced resource intensity and under arbitrary real-world driving conditions. The method relies upon the inference of instantaneous fuel consumption via the collection of OBD data and the simultaneous estimation of instantaneous engine output from vehicle dynamical behaviour.

Laminar burning velocity is a fundamental combustion property of any fuel/air mixture. Formulating gasoline fuel blends having faster burning velocities can be an effective strategy for enhancing engine and vehicle performance. Formulation of faster burning fuels by changing the fuel composition has been explored in this work leading to a clear correlation between engine performance and fuel burning velocity. In principle a gasoline vehicle should be calibrated to give optimal ignition timing (also known as MBT - minimum spark advance for best torque) while at the same time avoiding any possible engine knock. However, modern downsized/boosted engines frequently tend to be limited by knock and the spark timing is retarded in respect of the optimum. In such scenarios, faster burning fuels can lead to a more optimum combustion phasing resulting in a more efficient energy transfer and hence a faster acceleration and better performance.

It is expected that the world's energy demand will double by 2050, which requires energy-efficient technologies to be readily available. With the increasing number of vehicles on our roads the demand for energy is increasing rapidly, and with this there is an associated increase in CO₂ emissions. Through the careful use of optimized lubricants it is possible to significantly reduce vehicle fuel consumption and hence CO₂. This paper evaluates the effects on fuel economy of high quality, low viscosity heavy-duty diesel engine type lubricants against mainstream type products for all elements of the vehicle driveline. Testing was performed on Shell's driveline test facility for the evaluation of fuel consumption effects due to engine, gearbox and axle oils and the variation with engine operating conditions.

A predictive model for estimating the fuel saving of “top tier” engine, axle and transmission lubricants (compared to “mainstream” lubricants), in a heavy duty truck, operating on a realistic driving cycle, is described. Simulations have been performed for different truck weights (10, 20 and 40 tonnes) and it was found that the model predicts percentage fuel economy benefits that are of a similar magnitude to those measured in well controlled field trials1. The model predicts the percentage fuel saving from the engine oil should decrease as the vehicle load increases (which is in agreement with field trial results). The percentage fuel saving from the axle and gearbox oils initially decreases with load and then stays more or less constant. This behaviour is due to the detailed way in which axle and gearbox efficiency varies with speed/load and lubricant type.

A series of viscous and surface friction modifier additives has been studied in a modified SI engine with separable valve train lubrication. From the results, it has been possible to classify the hydrodynamic or boundary lubrication nature of the observed effects for a series of lubricant additives. It is shown that the frictional benefit of a given additive depends not only on the engine operating condition but also on the engine components on which it is acting. For some additives a fuel economy benefit can switch to a disbenefit as operating regime changes and a different aspect of the additive properties becomes important. Such observations are rationalised in the context of conventional lubrication theory.

Due to the recent drive to reduce CO₂ emissions, the turbocharged direct injection spark ignition (turbo DISI) gasoline engine has become increasingly popular. In addition, future turbo DISI engines could incorporate a form of charge dilution (e.g., lean operation or external EGR) to further increase fuel efficiency. Thus, the conditions experienced by the fuel before and during combustion are and will continue to be different from those experienced in naturally aspirated SI engines. This work investigates the effects of fuel properties on a modern and prototype turbo DISI engine, with particular focus on the octane appetite: How relevant are RON and MON in predicting a fuel's anti-knock performance in these modern/future engines? It is found that fuels with high RON and low MON values perform the best, suggesting the current MON requirements in fuel specifications could actually be detrimental.

GTL (Gas-To-Liquid) fuel is well known to improve tailpipe emissions when fuelling a conventional diesel vehicle, that is, one optimized to conventional fuel. This investigation assesses the additional potential for GTL fuel in a GTL-dedicated vehicle. This potential for GTL fuel was quantified in an EU 4 6-cylinder serial production engine. In the first stage, a comparison of engine performance was made of GTL fuel against conventional diesel, using identical engine calibrations. Next, adaptations enabled the full potential of GTL fuel within a dedicated calibration to be assessed. For this stage, two optimization goals were investigated: - Minimization of NOx emissions and - Minimization of fuel consumption. For each optimization the boundary condition was that emissions should be within the EU5 level. An additional constraint on the latter strategy required noise levels to remain within the baseline reference.

Building on two decades of expertise, a fourth generation fleet test protocol is presented for assessing the response of engine performance to gasoline additive treatment. In this case, the ability of additives to remove pre-existing deposit from the intake systems of port fuel injected vehicles has been examined. The protocol is capable of identifying real benefits under realistic market conditions, isolating fuel performance from other effects thereby allowing a direct comparison between different fuels. It is cost efficient and robust to unplanned incidents. The new protocol has been applied to the development of a candidate fuel additive package for the North American market. A vehicle fleet of 5 quadruplets (5 sets of 4 matched vehicles, each set of a different model) was tested twice, assessing the intake valve clean-up performance of 3 test fuels relative to a control fuel.

Addition of nitroalkanes to gasoline is shown to reduce the octane quality. The reduction in the Motor Octane Number (MON) is greater than the reduction in the Research Octane Number (RON). In other words addition of nitroalkanes causes an increase in octane sensitivity. The temperature of the compressed air/fuel mixture in the MON test is higher then in the RON test. Through chemical kinetic modelling, we are able to show how the temperature dependence of the reactions responsible for break-up of the nitroalkane molecule can lead to an increase in octane sensitivity. Results are presented from an Homogenous Charge Compression Ignition (HCCI) engine with a homogeneous charge in which the air intake temperature was varied. When the engine was operated on gasoline-like fuels containing nitroalkanes, it was observed that the combustion phasing was much more sensitive to the air intake temperature. This suggests a possible means of controlling combustion phasing for HCCI.

In this study, the influence of gasoline composition on exhaust emissions has been evaluated using three gasoline vehicles. Although the vehicles were obtained within Europe, each is representative of models to be found in Asian markets. Two of the vehicles were current Euro 4 certification, while the third was of Euro 2 certification equivalent to that available in specific Asian markets. Fuel effects studied included aromatics, olefins and benzene content. Other fuel properties were held constant within the normal constraints of blending when using realistic gasoline components. An orthogonal matrix of eight fuels was blended to evaluate these properties over the ranges: Aromatics (excluding benzene) 34% to 49%, olefins 18% to 25% and benzene 1% to 5%. All fuels were tested in all three cars driving the current legislative NEDC cycle, using a randomised block design with at least 3 repeats on each fuel/vehicle combination.

Reduction of exhaust emissions was investigated in a modern diesel engine equipped with advanced diesel after treatment system using a Gas-to-Liquid (GTL) fuel, a cleaner burning alternative diesel fuel. This fuel has near zero sulfur and aromatics and high cetane number. Some specially prepared GTL fuel samples were used to study the effects of GTL fuel distillation characteristics on exhaust emissions before engine modification. Test results indicated that distillation range of GTL fuels has a significant impact on engine out PM. High cetane number also improved HC and CO emissions, while these fuel properties have little effect on NOx emissions. From these results, it was found that low distillation range and high cetane number GTL fuel can provide a favorable potential in NOx/PM emissions trade-off. In order to improve the tail-pipe emissions in the latest diesel engine system, the engine modifications were carried out for the most favorable GTL fuel sample.

The accurate confirmation of fuel economy benefits arising from the use of a gasoline additive package is a difficult exercise. In order to fully understand, and accurately quantify, the interaction between the treated fuel and the engine it is necessary to carry out a fleet test which allows the benefit to be measured precisely yet under realistic conditions. A series of road tests, based on a ‘paired fleet’ design, has been carried out over the last two decades. Careful analysis of the results of these tests has led to the design of a new fleet testing protocol based around ‘quads’ rather than pairs of vehicles. This new test protocol also incorporates advances in vehicle selection and preparation procedures and has resulted in a test that is both more robust and flexible, and that achieves even better resolution than before.

Reduction of vehicle exhaust emissions is an important contributor to improved air quality. At the same time demand is growing for new transportation fuels that can enhance security and diversity of energy supply. Gas to Liquids (GTL) Fuel has generated much interest from governments and automotive manufacturers. It is a liquid fuel derived from natural gas, and its properties - sulphur free, low polyaromatics and high cetane number - make it desirable for future clean light-duty diesel engines. In this paper, the effects of distillation characteristics and cetane number of experimental GTL test fuels on direct injection (DI) diesel combustion and exhaust emissions were investigated, together with their spray behaviour and mixing characteristics. The test results show that the lower distillation test fuels produce the largest reductions in smoke and PM emissions even at high cetane numbers. This is linked to the enhanced air/fuel mixing of the lighter fuel in a shorter time.

Lubricant samples were aged on a SI bench engine that was run using ten different gasoline fuels. For each gasoline tested, the oxidative stability of the lubricant and the extent of engine wear was assessed in terms of a number of different parameters. Surprisingly, it was found that fuels containing higher levels of olefin (whether C8 olefin, or a C5/C6 olefin blend, or a catalytically cracked refinery stream) performed directionally better than a reference gasoline with low levels of aromatics and olefins. Fuels with a higher final boiling point and higher aromatic content, appeared to be associated with enhanced levels of sludge formation than the reference gasoline, but did not give rise to enhanced engine wear.

The effect of sulphur on a rhodium reformer catalyst was determined in the partial oxidation of n-heptane. The yield loss of the catalyst upon sulphur addition appeared to almost instantaneous and not progressive in time (i.e. it reaches a plateau). Up to ppm levels, the direct yield loss appeared to be linearly related to the sulphur level in the fuel and is of the order of around 3% per ppm of sulphur in the fuel. Sulphur adsorption on rhodium catalyst sites was found to be reversible. The original activity of the catalyst was quickly restored when changing to a sulphur free fuel. The effect of sulphur on the rhodium catalyst does not depend on the structure of the sulphur species. Based on this work, a 10 ppm sulphur maximum seems to be a sufficiently tight specification with respect to the stability of an appropriate reformer catalyst. By contrast, the presence of other species in fuels can cause irreversible and progressive catalyst deterioration.

Shell was the first oil marketer to bring to commercial scale, Gas to Liquids (GTL) technology for fuels and base oils production. This started with the commissioning of the multi-purpose GTL facility at Bintulu, Malaysia in 1993. The plant produces both automotive gas oil (GTL Fuel) as well as a number of speciality products including detergent feedstocks, a range of Fisher-Tropsch commercial wax grades, and a feedstock for base oils production. The base oil feedstock has been shipped to Shell facilities in Japan and France since 1994 where it is solvent de-waxed to produce the first commercially available GTL base oils. The GTL Fuel is currently being used in premium diesels in Germany, Greece and Thailand. Shell has announced in 2003 its intention to build two world scale GTL trains in Qatar and this will include substantial fuels and base oils facilities.

The introduction of sulphur-free fuels will enable advanced engine and exhaust after-treatment technologies to meet increasingly stringent exhaust emissions regulations. As these cleaner fuels and vehicles are introduced, the potential for further improvements in air quality through changes to fuel properties can be expected to diminish. Nevertheless, CONCAWE has continued to update knowledge by evaluating fuel effects on emissions from new engine/vehicle technologies as they approach the market. In this work, carried out as part of CONCAWE's contribution to the EU “PARTICULATES” consortium [1], two advanced light-duty diesel vehicles and three heavy-duty diesel engines covering Euro-3 to Euro-5 technologies, were tested. The fuels tested covered a range of sulphur content and compared conventional fuels with extreme fuel compositions such as Swedish Class 1 and Fischer Tropsch diesel fuels.

The Coordinating European Council, CEC, develops performance tests for the motor, oil, petroleum, additive and allied industries. In recent years, CEC has moved away from using round robin programmes (RRP's) for monitoring the precision and severity of test methods in favour of regular referencing within a test monitoring system (TMS). In a TMS, a reference sample of known performance, determined by cross-laboratory testing, is tested at regular intervals at each laboratory. The results are plotted on control charts and determine whether the installation is and continues to be fit to evaluate products. Results from all laboratories are collated and combined to monitor the general health of the test. The TMS approach offers considerable benefits in terms of detecting test problems and improving test quality. However, the effort required in collating data for statistical analysis is much greater, and there are technical difficulties in determining precision from TMS data.

Because reformer technology can be used in conjunction with advanced internal combustion engine technology, it is important to be able to formulate fuels that are compatible with both reformers and ICEs It has been found that most hydrocarbon species typically present in gasoline can be reformed with relative ease. The exception is that olefinic species of carbon number 6 and above are relatively much harder to reform. It is shown how a reformer compatible gasoline fuel with high octane can be blended. For Diesel fuels, synthetic ‘Gas to Liquid’ fuels are generally less susceptible to coking and hence superior to petroleum-derived fuels, for use with an onboard reformer.

The influence of gasoline quality on exhaust emissions has been evaluated using four modern European gasoline cars with advanced features designed to improve fuel economy and CO2 emissions, including stoichiometric direct injection, lean direct injection and MPI with variable valve actuation. Fuel effects studied included sulphur content, evaluated over a range from 4 to 148 mg/kg, and other gasoline properties, including aromatics content, olefins content, volatility and final boiling point (FBP). All four cars achieved very low emissions levels, with some clear differences between the vehicle technologies. Even at these low emissions levels, all four cars showed very little short-term sensitivity to gasoline sulphur content. The measured effects of the other gasoline properties were small and often conflicting, with differing directional responses for different vehicles and emissions.