The six persons, all residents of Haryana, were returning home after offering prayer at Salasar Temple when the speeding tanker rammed into their car near Ramnagar crossing on Churu bypass.
Shakuntala Yadav (67), Ramavtar Yadav (50), Virendra Yadav (54) and his wife Rekha Bai (48) died on spot while Saurabh Yadav (25) died while undergoing treatment.
Six-year-old Gaurav Yadav was referred to Hisar district for treatment, Churu Sadar police said.
The bodies were handed over to family members for last rites after post-mortem.