For 1990-2009 cars

# ANTIFREEZE CONCENTRATION EFFECTS ON ALL ENGINES

#### MODELS AFFECTED: ALL ENGINES

Todays vehicles are designed to operate with a 50/50 solution of antifreeze and water for optimum cooling system performance. This 50/50 solution gives the correct cooling system balance of freeze protection, heat dissipation and corrosion protection.

When cooling systems are drained for any reason it is important that the correct concentration of antifreeze be maintained. Increasing or decreasing the antifreeze concentration from the desired mix can have undesirable effects on the system.

Listed here are some facts concerning antifreeze concentrations.

A 50/50 antifreeze mix increases cooling capacity about 15% over clear water.

Higher concentrations of antifreeze will lower the cooling capacity.

Maximum freeze protection of -92 deg F (-69 Deg C) is obtained at about 69% antifreeze. Higher concentrations actually raise the freeze point.

The freeze point of 100% antifreeze is about -8 DEG F (-22 DEG C).

Engine damage from freezing due to very high concentrations of antifreeze is not likely for two reasons.

1. High concentration solutions do not freeze to a solid but become a heavy slush.

2. High concentrations of antifreeze contract rather than expand at their freezing point.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.