Storage stability of "Class C Gasoil" (a heating oil sold in Spain, similar to British Class E light fuel oil) was investigated through consideration of the figures obtained over the course of one year for three of its parameters most characteristically used to assess its quality: density, kinematic viscosity and volatility features (distillation curve).\ For the duration of the research project, the fuel was stored in bottles made of translucent borosilicated glass at ambient temperature and away from light. Aliquots taken periodically from these samples were tested for density using the UNE-EN ISO 3675 standard, for kinematic viscosity using the UNE-EN ISO 3104 standard, and for their distillation curve using the UNE-EN ISO 3405 standard.