On board ethanol steam reforming represents a highly attractive pathway for energy recovery in combustion engines, as it converts exhaust waste heat into a hydrogen rich reformate that can be directly used as an additional fuel, thereby improving overall engine efficiency. Unlike most studies conducted in laboratory scale reactors, this work evaluates ethanol steam reforming in a medium scale reactor with geometry and dimensions suitable for direct integration into an engine exhaust line. After selecting an appropriate space velocity, the effects of temperature and steam‑to‑ethanol ratio (SER) on ethanol reforming have been explored. Two catalysts have been checked: a commercial Ni‑based catalyst typically used for methane reforming and a research Co‑based catalyst designed to maximize hydrogen yield at high operating temperatures. The temperature window (300–600 °C) was chosen based on experimental exhaust temperatures recorded in a single‑cylinder research engine. Complete ethanol conversion was achieved at 400 °C and above, whereas conversion dropped sharply at lower temperatures, more markedly for the cobalt catalyst. A notable energy gain (i.e., higher energy content in the reformate gas than in the fed ethanol) was observed above 500 °C; however, the nickel catalyst retained acceptable energy performance even at temperature as low as 400 °C. Hydrogen selectivity increased with temperature, reaching up to 70 % at 600 °C for both catalysts, although their sensitivities to operating parameters differed. The Co catalyst showed almost no dependence on SER but exhibited a pronounced loss in hydrogen production at 300 °C. In contrast, the Ni catalyst was highly sensitive to SER, requiring a high ratio of 13:1 to reach hydrogen selectivity comparable to cobalt at medium‑to‑high temperatures. The Ni catalyst also showed a much higher methane selectivity below 500 °C, at the expense of lower CO yield. Coke formation was quantified through actual reactor mass changes after extended operation, providing a more realistic assessment than estimations based on precursor species. Coke deposition peaked at intermediate temperatures, reflecting a balance between formation and gasification. The cobalt catalyst produced almost no coke at 600 °C, but deposition increased rapidly at lower temperatures, particularly under low SER. Nevertheless, coke was effectively removed during steam regeneration, producing mostly CO₂ and H₂ and thereby providing an additional energy gain