The antifreeze in the engine block coolant performs three very important jobs:
- prevents the coolant from freezing during cold weather
- raises the boiling temperature of the coolant to prevent overheating during hot weather
- fights corrosion.
Besides checking the level of the coolant periodically to make sure it isn’t low (which usually indicates a leak), the strength and condition of the antifreeze should also be checked.
Most vehicle manufacturers recommend a 50/50 mixture of water and antifreeze for normal freezing and boil over protection. Up to a 70/30 mixture of antifreeze and water can be used to maximize freezing protection, but higher concentrations should not be used. Straight water or straight antifreeze should never be used in a vehicle’s cooling system.
Determining the condition of the coolant is a little more difficult because appearances alone can be deceiving. If the coolant is brown and discolored, it’s obviously long overdue for a change. But even if it’s still green, there’s no way to tell how much corrosion protection is still in the coolant without measuring its “reserve alkalinity.” This can be done with chemically-treated test strips that give a good-bad indication by color changes.
We recommend changing the coolant every two to three years or 30,000 miles to replenish the corrosion inhibitors in the antifreeze. If the cooling system is dirty, use a flush to remove rust and scale.