The present work deals with the fabrication of undoped lanthanum chromium oxide and indium doped lanthanum chromium oxide material by cost effective sol–gel method. The four sensors were fabricated by screen printing technique. The indium ion concentration was varied for LaCrO3 material from 0.1 M% to 0.7 M% to access the comparative gas sensing results. All the prepared materials were characterized by XRD, SEM, EDAX, TEM and IR to confirm their structural and chemical composition. The prepared sensors viz. 0.1 M% In3+ doped LaCrO3, 0.3 M% In3+ doped LaCrO3, 0.5 M% In3+ doped LaCrO3 and 0.7 M% In3+ doped LaCrO3 were investigated for gas sensing mechanism for selected gases such as petrol vapours, ethanol, ammonia, NO2, H2S and CO2 gases. The optimum response was recorded for tested gases for all the prepared sensors. The 0.3 M% In3+ doped LaCrO3 found to be exceptional for petrol vapour and highest response was recorded for petrol vapors for 0.3 M% In3+ doped LaCrO3 thick film sensor. All the indium doped are found to be good sensors for petrol vapours and moderate for other tested gases. The prime parameters for the sensors such as selectivity, response and recovery and reproducibility were recorded for the prepared sensor. The response and recovery was very rapid for 0.3 M% In3+ doped LaCrO3 sensor. The gas sensing mechanism for petrol vapours has been established for 0.3 M% In3+ doped LaCrO3 sensor via hole accumulation layer mechanism. The Schematic abstract exhibits the synthesis of In-doped LaCrO3 (0.1M%. 0.3M%, 0.5M% and 0.7M %) by the sol-gel manner. It also illustrates the characterization and optimal gas response to volatile petrol vapors among all the gases.