ISO 8178-5:2021

Overview

ISO 8178-5:2021 specifies test fuels recommended for measuring exhaust emissions from reciprocating internal combustion engines. It supports the test cycles defined in ISO 8178-4 and applies to engines for mobile, transportable and stationary installations - for example, earth‑moving machines and generating sets - but excludes on‑road vehicle engines. The fourth edition (2021) updates reference fuels (including EU Regulation 2017/654 fuels) and adds CARB and US EPA Tier 3 E10 certification fuels, with fuel specification updates aligned to ISO 8217.

Key Topics

• Choice of fuel: guidance on selecting appropriate reference or commercial fuels for emission testing and when to use analytical data sheets for reporting commercial fuels.
• Influence of fuel properties on emissions: discussion of how sulfur content, cetane/cetane index, octane/methane number, oxygenates and other properties affect emissions from compression‑ignition and spark‑ignition (SI) engines.
• Fuel categories covered:
  • Natural gas (reference, pipeline-admixed and non‑referenced)
  • Liquefied Petroleum Gas (LPG)
  • Engine gasolines (referenced and non‑referenced)
  • Diesel fuels (reference and commercial)
  • Distillate and residual fuel oils, crude oil, and alternative fuels
• Calculations and corrections: informative and normative annexes provide methods for fuel‑specific factors for exhaust flow, λ‑shift calculation, and correction for CO in exhaust due to CO in gaseous fuels.
• Normative references: ISO 8178‑1, ISO 8178‑4:2020, ISO 6974/6976, ISO 8217 and relevant EN and ASTM methods referenced for analyses and fuel definitions.

Applications

ISO 8178-5:2021 is used by:

• Engine manufacturers and R&D labs for standardized emission testing and development.
• Test laboratories performing ISO 8178 test cycles on off‑road, stationary or transportable engines.
• Regulatory and certification bodies assessing compliance with non‑road emission regulations.
• Fuel suppliers and fleet operators evaluating fuel impacts on emissions and ensuring test reproducibility. Practical uses include type‑approval testing, comparative performance testing, fuel effect studies, and site testing where commercial fuels are used (with recommended reporting requirements).

Related Standards

• ISO 8178‑1 (test‑bed measurement systems)
• ISO 8178‑4:2020 (steady‑state and transient test cycles)
• ISO 8217 (marine fuels)
• ISO 6974 / ISO 6976 (natural gas composition and properties)
• EN 228, EN 15376, ASTM D4815 (fuel analysis and specifications)

Keywords: ISO 8178-5:2021, test fuels, exhaust emission measurement, reciprocating internal combustion engines, reference fuels, diesel, natural gas, LPG, ISO 8178-4.