Dodge 2005 Viper Owner's Manual page 185

Adding Coolant
When adding coolant, or refilling the system, a minimum
solution of 50% recommended HOAT ethylene glycol
engine coolant (antifreeze) and distilled water should be
used. Use higher concentrations (not to exceed 70%) if
temperatures below 34°F ( 37°C) are anticipated.
Use only high purity water such as distilled or deionized
water when mixing the water / antifreeze solution. The
use of lower quality water will reduce the amount of
corrosion protection in the engine cooling system.
NOTE: It is the owner's responsibility to maintain the
proper level of protection against freezing according to
the temperatures occurring in the area where the vehicle
is operated.
MAINTAINING YOUR VEHICLE 185
WARNING!
Never add coolant to the radiator when the engine is
overheated. Do not loosen or remove pressure cap to
cool overheated engine. The coolant is under pres-
sure and severe scalding could result.
Cooling System Pressure Cap
The cap must be fully tightened to prevent loss of
coolant, and to insure that coolant will return to the
radiator from the coolant reserve tank.
The pressure cap should be inspected and cleaned if there
is any accumulation of foreign material on the sealing
surfaces.
7