Base Gasoline Research Articles

Influence of Ethanol-Gasoline Fuel Fractions on Variable Compression Ratio Engine

Increase in demand of ethanol as blending fuel with gasoline is increasing. For noting the performance of the engine, experimentations are required to be done on engine, fuelled with various percentages of ethanol in gasoline. In this study, fuel fractions of ethanol and gasoline were taken for observing the performance of spark ignition engine. One-cylinder gasoline engine was used for conducting the experiments and to analyse the effects of ethanol-gasoline fuel fraction on performance of the engine. The engine was tested at Full Open Throttle condition. The load on the engine was changed by changing the load on Eddy Current Dynamometer to vary the engine speed from 1300 to 1700 rpm in the interval of 100 rpm. Gasoline is blended with ethanol to make five fuel fractions from 0 % ethanol (E0) to 40 % ethanol (E40) in gasoline at the interval of 10% by volume. Engine performance was observed at various Compression Ratio (CR) of the engine as 7,8,9 and 10. Calorific Value (CV) of the fuel fractions observed decreasing from E0 to E40 as CV of ethanol is less than base gasoline. Increase in Brake Specific Fuel Consumption was not very significant with rise in ethanol percentage. Power outputs in terms of Brake Power (BP) was increasing with increase in speed of the engine and observed decreasing with increase in ethanol percentage at constant CR. However various engine output parameters like BP, Mechanical Efficiency found decreasing with increase in fuel fractions ratio. Brake Thermal Efficiency (BTE) was observed decreasing with increase in fuel fractions. However, BTE was observed increasing with increase in CR.

Autoignition Characteristics of Ethers Blended with Low Cetane Distillates

The introduction of high cetane components has enabled the use of low cetane base gasoline in compression ignition engines. This study provides an understanding of the autoignition characteristics ...

Effects of dual-alcohol gasoline blends on physiochemical properties and volatility behavior

Biofuels can contribute to reducing greenhouse gas emissions from the transportation sector. Ethanol is the main additive for gasoline in the United States, and gasoline containing 10 vol% ethanol is the most commonly used transportation fuel. However, the vapor pressure of these blends is significantly higher than gasoline, which contributes to evaporative emissions. One way to circumvent this and other issues is to use a dual-alcohol approach, mixing lower (methanol or ethanol) and higher alcohols with gasoline to obtain a blend with a vapor pressure close to that of the base gasoline. The goal of this study was to evaluate the fuel potential of dual alcohol blends experimentally and theoretically. Ten dual-alcohol blends were tested at blending ratios from 10 to 80 vol%, with methanol and ethanol used as the lower alcohols and iso-butanol and 3-methyl-3-pentanol as the higher alcohols. The corresponding single alcohol-gasoline blends were also evaluated. For each blend, Reid vapor pressure, vapor lock protection potential, distillation curve, lower heating value, kinematic viscosity, and water tolerance at three temperatures were measured. A model of droplet evaporation was also applied to provide insights into the azeotropic volatility behavior and mixing/sooting potential of the blends. The results of this study show that it is advantageous to use dual-alcohol blends containing up to 40 vol% because they have the characteristics necessary for good performance in existing spark-ignition engines, particularly in terms of volatility, kinematic viscosity, and water tolerance. This study is the first to characterize matched vapor pressure, dual-alcohol blends over a wide blending range as drop-in fuels for conventional spark ignition engines. Furthermore, this was the first investigation of the fuel potential of iso-butanol in dual-alcohol blends and of 3-methyl-3-pentanol in single- and dual-alcohol blends.

Effect of Varying Fuel Injection Timing on Engine Performance of CNG Direct Injection in Retrofitted SI Engine

The study of engine performance under different fuel injection timing of a CNG direct injection engine was carried out in a retrofitted car engine. The experiment was performed on a 1297cc, 4-stroke, four cylinder SI engine having compression ratio 9. The base gasoline engine was converted into bi-fuel engine by installing both CNG port injection (CNG-PI) and CNG direct injection (CNG-DI) system in a single gasoline engine. The injection timing was varied from early injection (EI) timing at 220° BTDC to a late injection (LI) timing of 120° BTDC. The experimental study was limited by an engine speed upto 2700 rpm due to high thermal loading at higher speed. The results indicate that, the late injection timing 120° BTDC gives 10-12% higher brake power at a lower engine speed upto 1800 rpm as the volumetric efficiency is better at a lower speed. The optimal injection timing 160° BTDC produces higher performance over the entire speed range from 1200 rpm to 2500 rpm due to sufficient and optimum time available for preparation of CNG-air mixture. The early injection timing 210° BTDC gives very good engine performance for engine speed above 2700 rpm which accelerates better air-fuel mixing at a higher speed.

Methanol as an octane booster for gasoline fuels

Octane rating is an essential property for gasoline-type fuels because it is the major factor that determines the maximum compression ratio (CR) allowed in spark-ignition engines. In practice, a base gasoline, which is a mixture of various refinery streams, is dosed with octane-booster additives for meeting the minimum octane requirements set by regulation standards. Coal-based methanol is widely used in China as a gasoline octane-booster. In addition to its high octane rating, methanol’s cooling effect derived from its low latent heat and its high octane sensitivity also contribute to engine knocking suppression in spark-ignition direct-injection (DISI) engines. Thus, fully understand the role of methanol addition in gasoline is highly relevant to estimate the potential thermal efficiency gain for methanol blends. The novelty of this paper is that methanol’s chemical effect, cooling effects and octane sensitivity effects on engine knocking suppression are quantitatively converted to an effective octane index (EOI), a parameter for comprehensively describing the anti-knocking properties of a gasoline-type fuel. Then ΔEOI of methanol blends (EOI_blend − EOI_base) was used for estimating engine thermal efficiency gain in compression ratio (CR) matched DISI engines. Results suggest that methanol’s cooling effect is as significant as its high octane rating. For example, the cooling effect of methanol corresponds to 19 unit of octane in a blend with 70 vol% methanol (M70). The indicated thermal efficiency gain is up to 30% for M70 with RON81.1 base gasoline. The reduction in the lower heating value (LHV) of methanol blends lead to higher fuel consumption, which can be partially or even entirely offset by the improved indicated thermal efficiency. Overall, this paper highlighted the effectiveness of methanol as an octane and thermal efficiency booster.

Development of a reduced four-component (toluene/n-heptane/iso-octane/ethanol) gasoline surrogate model

The prospect of blending gasoline fuel with ethanol is being investigated as a potential way to improve the knock residence of the base gasoline. However, one of the drawbacks is a lack of proper understanding of the reason for the non-linear response of blending ethanol and gasoline. This non-linearity could be better understood by an improved knowledge of the interactions of these fuel components at a molecular level. This study proposed a highly reduced four-component (toluene/n-heptane/iso-octane/ethanol) gasoline surrogate model containing 59 species and 270 reactions. The model was reduced using the direct relation graph with expert knowledge (DRG-X) (Lu and Law, 20015; Lu et al., 2011) and isomer lumping method. The computational singular perturbation (CSP) analysis were performed to reduce the potential stiffness issues by accordingly adjusting the Arrhenius coefficients of the proper reactions. The model has been comprehensively validated against wide range of ignition delay times (IDT) and flame speed (FS) measurement data as well as compared against two representative literature models from Liu et al. (2013) and Wang et al. (2015). Overall, good agreements were observed between model predictions and experimental data across the entire research octane number (RON), equivalence ratio, pressure and temperature range. In addition, the model has also been coupled with the computational fluid dynamic (CFD) models to simulate the experimental data of constant volume reacting spray of a low-octane gasoline (Haltermann straight-run naphtha), and in-cylinder pressures and temperatures of a high-octane gasoline (Haltermann Gasoline) combustion in a heavy duty compression ignition engine. The coupled model can qualitatively predict the experimentally obtained data with an improved performance for PRF, TPRF, and TPRF-ethanol surrogates.

Assessment of the use of ethanol instead of MTBE as an oxygenated compound in Mexican regular gasoline: combustion behavior and emissions.

The energy reforms implemented in Mexico promote the use of ethanol in gasoline but exclude the country's ozone nonattainment areas oxygenated with methyl-tert-butyl ether (MTBE) in view that further scientific studies are required. To address a potential implementation scenario in areas of ozone high VOC-sensitive regimes, the impact on performance and emissions characteristics between the regular MTBE fuel available and a formulated gasoline containing 10% v/v ethanol having similar Reid vapor pressure (RVP) were compared in a single cylinder spark-ignited engine and a set of tier I vehicles. Included in the assessment were the "criteria" pollutants (THC, CO, and NOx), toxic compounds, and speciated hydrocarbons in order to calculate the ozone-forming potential (OFP). The change in combustion speed of ethanol fuel vs. regular gasoline seems to be small and depends mainly on base gasoline formulation. Vehicle dynamometer testing showed no statistically significant differences in the average THC, CO, and NOx results when comparing both fuels. Statistically significant differences were seen in total speciated hydrocarbons, total carbonyls emitted, the increases in acetaldehyde emissions, and the decreases in OFP with E10. The results show roughly 20% increase in evaporative emissions when E10 is used, but the OFP of the emissions is lower than that of the Metropolitan Area of Mexico City fuel (MAMC). The increase in the oxygen content using ethanol fuel seems to have no deleterious effect on the vintage of vehicles tested. Taking into consideration that the evaporative emissions standard in Mexico is less stringent than that in other countries, the substitution of the actual regular gasoline for ethanol fuels should uphold the least volatile AA class in areas with ozone problems.

Azeotrope formation in gasoline–ethanol blends. Part 1 – Impact of nonionic on E10 distillation curve

Blending 10 vol% of ethanol into hydrocarbon base gasoline (HBG) increases significantly the vapour pressure of the blend (E10), and exhibits near-azeotrope behaviour that severely affects the shape of E10 distillation curve. The distillation curves of HBG and E10 fuel blend, were constructed using ASTM D86 distillation data, and the areas under each distillation curve, were calculated through the numerical trapezoid rule (NTR) and calculus definite integration (CDI) methods. Consequently, the area due to azeotrope formation (ADAF), was estimated. In this paper, we present the impact of small concentration of nonionic surfactant on the area under distillation curve (AUDC) of E10 fuel blend and the area due to azeotrope formation (ADAF). Also, the influences of the added surfactant on the volatility criteria of the investigated E10 fuel blend were discussed.

Effects of Methyl Acetate as Oxygenated Fuel Blending on Performance and Emissions of SI Engine

Abstract - The objective of this paper is to investigate the use of methyl acetate as oxygenated fuel blending for base gasoline in SI engine. The effects of methyl acetate on engine performance parameters (brake specific fuel consumption, brake thermal efficiency and energy consumption rate) and exhaust emissions (CO, HC, CO2 and NOx) of SI engine have been experimentally investigated. Engine experiments were conducted on a single cylinder, water cooled, spark-ignition test engine at constant moderate speed; 1500 rpm for different loads; 104, 207, 311 and 414 kPa fuelling the engine with base gasoline, M5 (95 % base gasoline +5 % methyl acetate) and M10 (90 % base gasoline +10 % methyl acetate). The results showed that adding methyl acetate to base gasoline increases the brake specific fuel consumption while reducing the brake thermal efficiency of the engine. Furthermore, it was also observed that methyl acetate addition does not have a great effect on HC emissions, however, reduces CO and increases CO2 emissions. NOx results showed a striking increase in the level of NOx emissions with the addition of methyl acetate.

Evaluation on physicochemical properties of iso-butanol additives in ethanol-gasoline blend on performance and emission characteristics of a spark-ignition engine

In this study, experiments were conducted on a four-cylinder spark-ignition engine to investigate the effects of iso-butanol additives in ethanol-gasoline blend on fuel properties, performance and emission characteristics of a SI engine. The engine tests were carried out at 50% wide open throttle and variations of engine speed from 3000 to 5000 RPM with an interval of 1000 RPM. The engine was fueled with base gasoline fuel, ethanol-gasoline blended fuel at 10% volume percentage of ethanol (E10) and three different fuel blends of iso-butanol additives; 5%, 10% and 15%, in E10 blended fuel denoted as E10B5, E10B10 and E10B15, respectively. Physicochemical properties tests were conducted in this study to evaluate the fuel heating value, kinematic viscosity and density, which have been selected due to their influences on engine performance and exhaust emissions. Results of heating value showed a decreasing pattern for the blended fuel samples compared with that of base gasoline fuel as E10, E10B5, E10B10 and E10B15 produced 2.33%, 3.14%, 5.06%, and 5.31%, respectively. However, as alcohol concentration increases in the blended fuel samples, the density and kinematic viscosity were both increased with maximum values of 0.767 g/cm3 and 1.15 mm2/s, respectively obtained for E10B15. In terms of engine performance, the blended fuel samples exhibited higher brake power than that of base gasoline fuel with mean increase of 7.71%, 10.21%, 10.89% and 11.54% for E10, E10B5, E10B10 and E10B15, respectively. Significant reduction in brake specific fuel consumption obtained with E10, E10B5, E10B10 and E10B15 by mean of 3.57%, 5.15%, 7.14% and 10.89% respectively, compared to base gasoline fuel. Noticeable improvement of brake thermal efficiency observed with the blended fuel at a maximum increment of 18.91% achieved by E10B15. High combustion temperature produced by the blended fuel samples have been contributed to the higher exhaust gas temperature. Accordingly, the emissions of carbon monoxide and hydrocarbon were all reduced; except for carbon dioxide and nitrogen oxide, with the addition of iso-butanol additive compared to those of ethanol-gasoline blend and base gasoline fuel.

The effects of addition of co-solvents on the physicochemical properties of gasoline–methanol blended fuels

The scope of the work carried out is aimed to evaluate the effects of blending methanol in the gasoline pool, particularly octane number and Reid vapor pressure increase when methanol is substituting methyl-tertiary-butyl ether in the formulation of Regular and Premium base gasolines. Isopropyl alcohol and ethanol have been investigated and found to be a promising co-blending alcohol to be mixed in gasoline methanol blends. Isopropyl alcohol is most effective below 3 vol%. Ethanol has been found to be the most promising co-blending alcohol able to reduce the Reid vapor pressure increase by 1.4 psi even with concentrations in the range of 2 vol%. The addition of isopropyl alcohol to the methanol–gasoline blends has shown the ability of a ternary mixture to further reduce the Reid vapor pressure of the finished gasoline and, subject to availability and price of isopropyl alcohol, could be of interest in further formulation studies focused on maximizing the saving on finished gasoline cost by reducing the Reid vapor pressure of base gasoline and/or increasing the methanol content.

Part -3 - Azeotrope Formation and Distillation Curve of Gasoline – Alcohol Mixtures

Mixing of alcohol with hydrocarbon base gasoline causes an increase in the vapour pressure of the mixture .This is because alcohol (methanol or ethanol) combines with certain low molecular weight Hydrocarbons to form azeotropes.Azeotropes have lower boiling points than the hydrocarbons from which they are made, resulting in an increase in vapour pressure . This paper presents the estimation of the areas under the distillation curves of gasoline – methanol mixtures and that of the hydrocarbon base gasoline. Calculation of areas was carried out using the Numerical Trapezoid rule and Calculus Definite Integration method. Linear equations were developed relating the logarithmic values of the areas resulted from azeotrope formations and the alcohol concentrations , Also , correlation between azeotropic area and some volatility terms were discussed

Comparison of performance and emissions for gasoline-oxygenated blends up to 20 percent oxygen and implications for combustion on a spark-ignited engine

Although experimental studies have shown that alcohol fuels burn cleaner than unleaded gasoline, there is limited information regarding the comparison among the alcohol fuels as gasoline additive in spark-ignited engines. Therefore, in this work, twelve different fuel formulations varying base composition (three different base gasolines), oxygenated level (3.5wt% up to 20wt%) and oxygenating agent (i.e. ethers, alcohols and one carbonate) were burned in a spark-ignited engine (AVL 5401 SI single cylinder) engine electronically controlled to investigate the relationships between fuel formulation, engine performance and exhaust emissions at constant spark advance (without combustion phasing optimization). Fuel properties related to initial phases of evaporation i.e. Reid Vapor Pressure, T10, T50, and heat of vaporization suggested an important effects of mixture formation and fuel metering in the combustion development. Experimental results were supported by both direct analysis of test matrix and statistical analysis. Moreover, results indicated that oxygen content and specific gravity were directly associated with CO and CO2 emissions, and inversely associated with NOx emissions. Hydrogen fuel content was directly associated with NOx emissions and inversely with CO2. Naphthenes, iso-paraffins, T90, and final boiling point showed marginal effect on engine performance and emissions.

Optimization of the octane response of gasoline/ethanol blends

The octane responses of gasoline/ethanol mixtures are not well understood because of the unidentified intermolecular interactions in such blends. In general, when ethanol is blended with gasoline, the Research Octane Number (RON) and the Motor Octane Number (MON) non-linearly increase or decrease, and the non-linearity is determined by the composition of the base gasoline and the amount of added ethanol. The complexity of commercial gasolines, comprising of hundreds of different components, makes it challenging to understand ethanol-gasoline synergistic/antagonistic blending effects. Understanding ethanol blending effects with simpler gasoline surrogates is critical to acquire knowledge about ethanol blending with complex multi-component gasoline fuels. In this study, the octane numbers (ON) of ethanol blends with five relevant gasoline surrogate molecules were measured. The molecules investigated in this study include: n-pentane, iso-pentane, 1,2,4-trimethylbenzene, cyclopentane and 1-hexene. These new measurements along with the available data of n-heptane, iso-octane, toluene, various primary reference fuels (PRF) and toluene primary reference fuels (TPRF) with ethanol are used to develop a blending rule for the octane response (RON and MON) of multi-component blends with ethanol. In addition, new ON data are collected for six Fuels for Advanced Combustion Engine (FACE) with ethanol. The relatively simple volume based model successfully predicts the octane numbers (ON) of the various ethanol/PRF and ethanol/TPRF blends with the majority of predictions being within the ASTM D2699 (RON) and D2700 (MON) reproducibility limits. The model is also successfully validated against the ON of the FACE gasolines blended with ethanol with the majority of predictions being within the reproducibility limits. Finally, insights into the possible causes of the synergistic and antagonistic effects of different molecules with ethanol are provided.

Production of gasohol from isobutanol

Butanol is a four carbon chain alcohol compound of a non-polar used as a solvent and as an intermediate in several consumer products. It can be produced from petrochemical process route as well as biochemical process. A common petrochemical route to produce butanol is hydroformylation of propylene as primary feedstock followed by hydrogenation. The increasing demand for butanol and the scarcity of petrochemical basestock has put the urgent need for a renewable resource of butanol production. Biobutanol is butanol produced from renewable, biological feedstock through fermentation of plant materials types of food, non-food and biomass. One isomer of butanol which is more similar with gasoline property is isobutanol. The use of isobutanol is commonly as solvent in coatings industry, as lacquers, melamine or phenolic resin. Isobutanol can be potentially used as a gasoline blending component, and it is better than ethanol due to its higher heating value, lower volatility and less corrosive. A brief review of process technology for butanol production is outlined in this paper. The benefit of isobutanol over ethanol was also overviewed. In order to prove the compatibility on fuel application, the production of gasohol was carried out by mixing isobutanol and base gasoline, then evaluated according to commercial fuel specification. From the research work, it has been shown that the addition of isobutanol in base gasoline by certain volum fraction has met the typical fuel specifications used for spark-ignition engine. The physical and chemical properties of the mixture was quite similar to gasoline 88 and gasoline 92 specifications.

AN APPRAISAL OF THE FEASIBILITY OF GASOLINE PRODUCTION BY USING ALTERNATIVE ADDITIVES.

Toxic lead additives to gasoline are no longer used in many countries worldwide. The principle objectives of the present work are to upgrade the quality of some petroleum products through various operations. This study investigated the effect of alternative additives such as Methanol, MTBE on the 80 RON gasolines, light and heavy Naphtha via different blends of variable percentages. The CFR engine was employed to measure the Octane number of the produced blends while mixtures of other alternative additives were prepared and added to the previously mentioned blends. The obtained results showed that the additives have led to a significant improvement of the measured octane number of gasoline. Nevertheless, it was noted that decreasing the Methanol percentage had a negative effect on the environment. As illustrated by the results, it is noted that the gain in the research octane number in the methanol blended samples is higher than base gasoline. Also, the gaseous emissions produced on combustion such as carbon monoxide, nitric oxides and unburnt hydrocarbons have shown a noticeable decrease of 26% for unburnt, 16% for CO and 14.5 % for NOx. However, Carbon dioxide emissions have increased by 5.6 % which may are attributed to the complete combustion of the fuel on the expense of Carbon monoxide emissions. Moreover, the effect of oxygenate addition on the volume of air required to was detected in the decrease in the NOx emissions.

Performance and emissions of gasoline–dual alcohol blends in spark-ignited single cylinder engine

Three alcohols (ethanol, methanol and isobutanol), two ethers (ethyl tert-butyl ether and methyl tert-butyl ether) and dimethyl carbonate were blended in a base fuel at 3.5 wt % oxygen. Two of the fuels were dual alcohol–gasoline blends with methanol/ethanol and methanol/isobutanol having the same added volume of each alcohol. The performance was analyzed on a single spark-ignited engine. Emissions of nitrogen oxides, carbon monoxide, unburned hydrocarbons and carbon dioxide were monitored online. The dual-alcohol blends present higher cooling effect, power and thermal efficiency as well as low combustion cyclic dispersion and fast combustion. Combustion effects due to the addition of oxygenates can be attributed to base gasoline dilution, for a given oxygen content. Also, dilution increases the hydrogen proportion, and this seems to have a strong relationship with the observed increases in combustion duration.

Investigation of the effects of iso-butanol additives on spark ignition engine fuelled with methanol-gasoline blends

Alternative fuels on internal combustion engine (ICE) recently has become an attention due to the concern for environmental protection, and needs on reducing dependency on fossil fuels and meeting the current stringent regulation. Alcohol fuel is one of the attractive alternative fuels as it can be produced from renewable resources and is oxygenated. Methanol fuel is a well-known alcohol fuel that can be blended at the lower blending ratio with gasoline and produce better engine operation in spark ignition engine. However, there is a problem related to its methanol properties, especially on its energy content and vapour lock characteristics. Alcohol with higher carbon number such as iso-butanol has high energy content and is able to displace more petroleum gasoline compared to the methanol-gasoline blended fuel. In this study, the focus on the effect of the iso-butanol additive in the methanol-gasoline fuel of unmodified spark ignition engines. A lower ratio of methanol-gasoline blends (M5) was blended with the iso-butanol additive for 5 to 15% with 5% increment compared with base gasoline fuel. Tests were conducted at constant load (100%) with a variable of lower engine speed range from 1000rpm to 2500rpm. The results indicate that as for engine performance, M5B15 displayed improvement in engine brake power, BTE (brake thermal efficiency), and EGT (exhaust gas temperature) compared to other blended fuels. Nevertheless, there is a higher fuel consumption was recorded for all methanol-gasoline blended fuels with iso-butanol additive compared to base gasoline fuel. In terms of engine emissions, M5B15 gives a significant reduction in CO and HC emissions compared to base gasoline fuel. However, the increasing trend projected by NOx and CO2 emissions had been recorded in all iso-butanol additive in methanol-gasoline fuels with M5B15 exerting the highest emissions. It can be concluded that iso-butanol additives are a viable option to be blended with existing lower ratio of methanol-gasoline for spark ignition engine operation as an alternative fuel.

Fuel consumption of gasoline ethanol blends at different engine rotational speeds

Fuel consumption (mf kg/h) was estimated for two hydrocarbon gasolines (BG1-OE and BG2-OE) and their ethanol blends which contain from 4 to 20 vol.% of ethanol. Fuel consumption experiments for sixteen fuel samples (5L each), were conducted on a four cylinder, four stroke spark ignition test vehicle Sahin car, Type 1.45, model 2001. The engine has a swept volume of 1400 c.c., a compression ratio of 8.3:1 and a maximum power of 78 HP at 5500rpm. The obtained data reveal that the relation between fuel consumption and ethanol concentration is linear. Six linear equations for BG1-ethanol blends and BG2-ethanol ones at the investigated rotational speeds, were developed. Fuel consumption values of the first set of gasoline-ethanol blends are lower than that of the second set. This may be attributed to the difference in the chemical composition of base gasolines BG1 in the first set which is enriched in the less volatile reformate if compared with the second set which is more enriched in isomerate, the more volatile refinery stream.

A blending rule for octane numbers of PRFs and TPRFs with ethanol

Ethanol is widely used as an octane booster in commercial gasoline fuels. Its oxygenated nature aids in reducing harmful emissions such as nitric oxides (NOx), soot and unburned hydrocarbons (HC). However, the non-linear octane response of ethanol blending with gasoline fuels is not completely understood because of the unknown intermolecular interactions in such blends. In general, when ethanol is blended with gasoline, the Research Octane Number (RON) and the Motor Octane Number (MON) non-linearly increase (synergistic) or decrease (antagonistic), and the non-linearity depends on the composition of the base gasoline. The complexity of commercial gasoline, comprising of hundreds of different components, makes it challenging to understand ethanol–gasoline synergistic/antagonistic blending effects. Understanding ethanol blending effects with simpler gasoline surrogates blends may enable a better understanding of ethanol blending with complex multi-component gasoline fuels. This study presents a blending rule to predict the octane numbers (ON) of ethanol/primary reference fuel (PRF; mixtures of iso-octane and n-heptane) and ethanol/toluene primary reference fuel (TPRF; mixtures of toluene, iso-octane and n-heptane) mixtures using the data available in literature and new data. The ON of ethanol blends with PRF-40, -50, and -60 were measured and compared with those from literature. Additional experimental data were collected to validate the developed model for ethanol blends of three different TPRFs having the same RON but different MON (i.e., different toluene contents). The three tested TPRF mixtures have octane ratings of RON 60.0/MON 58.0 (toluene 10.2vol%), RON 60.0/MON 56.3 (toluene 19.8vol%), and RON 60.0/MON 53.2 (toluene 40.2vol%). The octane prediction model consists of linear and non-linear by mole regions. The transition point between the linear and non-linear regions is a function of the RON and MON of the base PRF and TPRF mixture. The non-linear by mole region is defined as a second-order polynomial and the combined model successfully predicts the octane number (ON) of the various ethanol/PRF and ethanol/TPRF blends with a maximum ON error of 2.7, with the majority of predictions being within the reproducibility limits. Finally, the model presented here is shown to be an improvement over that existing already in the literature.