Millimeter-sized crystalline particles of butyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, C21H34O3, magnitudes larger than adherent particulate matter commonly observed during routine filter service inspections, were found in a commercial bus engine running on compressed methane biofuels and subjected to single-crystal XRD investigation. The structure is fully ordered and shows molecules in rather extended conformations being linked into chains by O—H...O hydrogen bonds.
