Eco-mortars have emerged as a sustainable alternative to conventional cement-based mortars by incorporating bio-based materials aiming to reduce the environmental impact. This study investigates the development of eco-mortars through the substitution of the cementitious binder by incorporating vegetal oils, focusing on the saponification reaction. The study analyzes the influence of oil dosage on fresh-state properties, hydration processes and physical–mechanical performance. The research comprehends the mechanical characterisation (bending, compression and ultrasound analysis) of eco-mortar conducted in samples with different 3 ratio of aggregate-binder, 2 ratio of CaO and the internal ratio of filler-sand (aggregates) and RACO (eco-binder, ricinoleic acid ”RA” and castor oil ”CO”), resulting in a total of 29 different combination of mortar mixes. Experimental results demonstrate that the optimal ratio is 85% aggregate and 15% eco-binder with a 50% of ricinoleic acid, obtaining mechanical properties of 3,9 MPa compression strength and 2,1 MPa bending strength. The findings highlight the potential of vegetable oil as a substituted for cement in eco-friendly mortar for low structural performance applications.