TATA Motors Indigo Owner's Manual & Service Book - page 148
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Coolants :
Presence of dirt in the coolant chokes up passages in the
radiator, cylinder head and cylinder block, thereby causing
insufficient cooling of engine.
To prevent rust formation and freezing of coolant inside the
passages of radiator, cylinder block and cylinder head,
use only branded premixed engine coolant.
IMPORTANT INFORMATION - Fuel, Lubricants & Coolant