FORD 2003 Ranger - Manual (Page 203)

Your vehicle was factory-filled with a 50/50 engine coolant and water
concentration. If the concentration of coolant falls below 40% or above
60%, the engine parts could become damaged or not work properly. A
50–50 mixture of coolant and water provides the following:
• Freeze protection down to -36° C (-34° F).
• Boiling protection up to 129° C (265° F).
• Protection against rust and other forms of corrosion.
• Enables calibrated gauges to work properly.
• 2.3L engines
• 3.0L and 4.0L engines
When the engine is cold, check the level of the engine coolant in the
reservoir.
• The engine coolant should be at the “cold fill level” or within the “cold
fill range” as listed on the engine coolant reservoir (depending upon
application).
RADIATOR
COOLANT
ONLY
Maintenance and Specifications
203