Driverability Index of Gasoline

The gasoline driveability index is a measure of the performance of gasoline fuel in internal combustion engines and has significant implications for engine performance and emissions. A higher driveability index indicates that the fuel is likely to perform better in terms of starting, idling, acceleration, and power, while a lower index indicates poorer performance.

It is typically used by gasoline producers and fuel quality regulators to ensure that gasoline meets certain minimum standards for performance and emissions.

Significance of the Drievebility Index

The significance of the driveability index can be seen in several areas;

1. Engine performance

The driveability index is used by engine manufacturers to develop engines that are optimized for specific types of gasoline. It can help them determine the best fuel properties for achieving optimal performance, such as the ideal volatility and density.

2. Emissions

The driveability index can also have an impact on emissions from internal combustion engines. For example, fuels with a higher driveability index may produce lower levels of pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (UHC), because they are more easily and completely combusted.

3. Fuel Economy

The driveability index can also affect fuel economy, as fuels with a higher index may provide more efficient combustion and better engine performance, leading to improved fuel efficiency.

4. Consumer choice

The driveability index can help inform consumers’ choices about which type of gasoline to use in their vehicles. By selecting a fuel with a higher driveability index, consumers can potentially achieve better engine performance and fuel efficiency.

Calculations of the Driveability Index

The driveability index is a measure of a gasoline’s performance across a number of operating conditions, covering cold start and warmed-up operations. It incorporates elements of the distillation profile for the gasoline (temperatures for evaporation percentages, such as T50) as well as ethanol content.

Driveability Index (DI) = 1.5 T₁₀ + 3.0 T₅₀ + 1.0 T₉₀ + 1.33 °C (2.4 °F) × Ethanol Volume %,

Where T10, T50, and T90 are the temperatures at which 10%, 50%, and 90% of volume boils off, respectively.

or for Degrees Fahrenheit & Degrees Centigrade

DI ( °C) = 1.5x(T10) + 3.0x(T50) + (T90) + 1.33x(Vol % ethanol)

DI (°F) = 1.5x(T10) + 3.0x(T50) + (T90) + 2.4x(Vol % ethanol)

Example: Gasoline fuel Driveability Index Calculations

T10= 142 °F, T50= 221 °F, T90= 340 °F , Ethanol= 15 % Vol.

Driveability Index= 1.5*142+3*221+340+2.4*15= 1256 °F

The proposed ASTM limit for driveability index is 1250°F (597°C) and 1200°F (569°C) for summer and winter seasons respectively.

Driveability Index Applications

The Driveability Index is useful for comparing the performance of different gasoline blends or formulations and for evaluating the effectiveness of fuel additives in improving drivability. A higher DI value indicates better overall driveability performance, with lower levels of engine problem, hesitation, and roughness.
The DI is used primarily as a quality control measure for gasoline. By ensuring that gasoline meets minimum performance standards for emissions, and engine protection, the DI can help reduce the occurrence of engine damage, knock, and other problems that can result from using low-quality fuel.
In addition, the DI can be used to optimize fuel formulations for specific engine types and operating conditions. Gasoline producers can adjust the fuel properties that contribute to the DI to create fuels that are better suited for high-performance engines, cold weather conditions, or other specific applications.