Over the last years extensively research has been carried out on full or partial substitution of supplies resources coming from renewable resources on traditionally non-renewable, in the case of the automobile sector there are progresses in bio-combustibles (biofuel) and synthetic oils coming from vegetable sources. There are strong efforts to find oil additives which can improve oils features in automobile industry, by adding vegetables oils to commercial lubricant oils, is expected to improve oil thermal stability. In the present research, different ratios of castor oil (ricinus comunis)-motor oil blends were obtained and their thermal properties were characterized by using the so-called Back and Front Photopyroelectric (BPPE/FPPE) techniques. Several oil-additives concentrations were measured and thermal diffusivities and effusivities as well as densities are reported, getting full thermal characterization for every concentration