It is well known that the addition of gaseous fuels to the intake manifold of diesel engines can have significant benefits in terms of both reducing emissions of hazardous gases and soot and improving fuel economy. Particularly, the addition of LPG has been investigated in numerous studies. Drawbacks, however, of such dual fuel strategies can be found in storage complexity and end-user inconvenience. It is for this reason that on-board refining of a single fuel (for example, diesel) could be an interesting alternative. A second-generation fuel reformer has been engineered and successfully tested. The reformer can work with both gaseous and liquid fuels and by means of partial oxidation of a rich fuel-air mix, converts these into syngas: a mixture of H₂ and CO. The process occurs as partial oxidation takes place in an adiabatic ceramic reaction chamber. High efficiency is ensured by the high temperature inside the chamber due to heat release. Thus, efficient thermal insulation is crucial to maintain said temperature. Heat recuperation from the reformer exhaust also improves the thermal efficiency. The prototype yields up to 20% of H₂ (80% of the theoretical maximum) and 22% of CO with all kinds of fuels tested, including automotive diesel fuel. Efficient thermal insulation allows to keep the dimensions below 40 cm in any direction for a full burning power of 10-30 kW while outer wall of the reformer is exposed to air at normal temperature.