Modifying Coolant Protection
If your hydrometer test indicates the freezing point of the coolant is too high and must be reduced, some coolant will need to be drained from the system and replaced with pure antifreeze. This will increase the overall antifreeze concentration and reduce the coolant's freezing point (that is, improve low temperature protection).
Use the graph below to determine the portion of the system to drain. Select the desired freezing point on the horizontal axis. Identify the line that most nearly represents your coolant's current freezing point, then read the replacement fraction given on the vertical axis. Multiply this fraction (decimal) by your cooling system capacity to determine the actual volume to replace.
For example, if your coolant has a current freezing point of +10° F. and you wish to reduce this to -30° F., observe that -30° F. on the horizontal axis and the middle (yellow) line intersect at 0.25 on the vertical axis. Therefore, approximately 4 quarts of coolant would need to be drained and replaced with pure antifreeze for a 16 qt. system, since 16 qt. x 0.25 = 4 qt.
SYSTEMS
COOLANT
DETERMINING COOLANT PROTECTION
CORRECT OPERATION