The primary differences between the different brands of antifreeze are the type and/or quantity of anti-corrosion additives that are used. Ethylene glycol is the primary component of anti-freeze, and this never wears out but the anti-corrosion additives do. That’s one reason why antifreeze should be changed every two years (except for long life antifreezes, which have special additive packages that allow them to go up to 5 years/150,000 miles between changes). For the environmentally concerned, propylene glycol (PG) antifreeze is also available at slightly higher cost. PG antifreeze is less toxic than ethylene glycol. Remember that ethylene glycol is a hazardous waste and should not be allowed to enter the storm drain system.
Taskers Automotive has a special machine that uses a vacuum to completely remove all the old corrosive antifreeze before replacing it with fresh antifreeze.