Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5798-21 – Standard Test Method Technical Guide
🌿 Scope and Composition of D5798-21
ASTM D5798-21 establishes the requirements for automotive ethanol fuel blends intended for use in ground vehicles equipped with flexible-fuel spark-ignition engines. The standard defines a fuel blend containing 51 % to 83 % by volume ethanol, commonly referred to at retail as “Ethanol Flex-Fuel.” Formerly designated as Fuel Ethanol (Ed70-Ed85) and known commercially as E85, the nomenclature was revised to “Ethanol Fuel Blends” to prevent confusion with denatured fuel ethanol (Specification D4806).
A critical aspect of this specification is the seasonal adjustment of vapor pressure. To ensure adequate cold-start operability, vapor pressure is increased during colder months. This is achieved by the blender through adjustments in ethanol content and the selection of hydrocarbon blendstock to meet the required vapor pressure parameters.
💡 Historical Context: The standard was previously titled “Fuel Ethanol (Ed70-Ed85) for Automotive Spark-Ignition Engines.” The shift to “Ethanol Fuel Blends” and the establishment of a lower minimum ethanol content (51 %) facilitates blending that meets seasonal vapor pressure requirements while maintaining compatibility with flexible-fuel vehicles.
📋 Summary of Key Compositional Requirements
| 🟦 Key Parameter | 📏 Specification / Requirement |
|---|---|
| Ethanol Content | 51 % to 83 % by volume |
| Intended Use | Flexible-Fuel Automotive Spark-Ignition Engines |
| Retail Label | “Ethanol Flex-Fuel” |
| Vapor Pressure | Varied for seasonal climatic changes |
| Former Nomenclature | Fuel Ethanol (Ed70-Ed85) / E85 |
⚙️ Referenced Quality Control Standards
Compliance with D5798−21 requires testing against a defined set of ASTM methods to ensure fuel quality, stability, and non-corrosiveness. The following table summarizes the primary test methods incorporated by reference in Section 2.
| 🟦 Property / Test | 📏 ASTM Standard | 🎯 Purpose |
|---|---|---|
| Distillation Profile | D86 | Determines volatility characteristics |
| Copper Strip Corrosion | D130 | Measures corrosiveness to fuel system components |
| Gum Content | D381 | Controls evaporation residue from fuel degradation |
| Oxidation Stability | D525 © 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence. 📥 Standard Documents Download |