Thread: Green Coolant
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Old 12-11-2003, 12:22 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
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There are three major types of antifreeze that make up about 99+ percent of the market. All use an ethylene glycol base, but have different corrosion inhibitor chemistry. The two primary functions of antifreeze are to provide lower freezing and higher boiling points and protect the system from corrosion. This is why there is a change interval. The corrosion inhibitor package is consumed with time, and the clock runs regardless of whether the car is operated or not, which is why many OE antifreeze change recommendations on a mileage/time interval, WHICHEVER COMES FIRST.

The three types of corrosion inhibitor packages are inorganic, organic, and hybrid. The green stuff uses an inorganic package, which contains a lot of phosphates and silicates. These provide good corrosion protection, but tend to precipitate out and plug radiator tubes, so instead of corroding through, the system eventually gets plugged up. The silicates are also abrasive, which can shorten coolant pump life.

One of the first organic inhibitor packages that was widely adopted is GM Dexcool. After reading about this new technology in the mid-nineties, which provides excellent corrosion protection, does not precipitate out salts that plug the system, and is non abrasive to the coolant pump seals, I switched all my cars to Dexcool before it was widely available. I bought Havoline Extended Life Antifreeze directly from Texaco who manufactures the product for GM. You can now buy Dexcool at normal retail outlets from several manufacturers.

Hybrid systems have been around for a long time and have been used by European manufactures since at least the early eighties if not earlier. Hybrids use a basic organic inhibitor package, but have a very small does of inorganics such as silicates, which is where the name "hybrid" is derived. The MB coolant is a hybrid as is Zerex G-05, which is a development of the hybrid that MB used in the eighties, but is now available at a reasonable price at auto parts stores, and is the same as current MB antifreeze.

I don't recommend green stuff in ANY car, but when changing from green stuff to either Dexcool or G-05, the system should be thoroughly drained and flushed as there is some incompatibility between the corrosion inhibitor packages and mixing them can reduce corrosion protection.

Drain the system thoroughly by opening all drains to include the radiator, block, and any others. Once drained remove the heater core inlet hose at the head nipple and flush the heater core circuit and engine thoroughly with a garden hose until the effluent is colorless and tasteless. It's also not a bad idea to do a couple of hot flushes by filling the system with potable water, then starting the engine and allowing to to operate until the thermostat is open for about five minutes. Drain and let the engine cool then repeat the process. After all this any traces of the green stuff should be essentially removed.

Fill the system with a 50/50 mix of either Dexcool or G-05 with distilled water.

MB's recommended drain interval for my '88 190E, assuming the use of MB antifreeze or equivalent (G-05 and Dexcool can be consider equivalent for maintenance interval purposes) is three years, with NO MILEAGE LIMIT!!!

I'd be interested in hearing if they still recommend the same maintenance interval for recent model years. It should be in the owner's packet recommended maintenance schedule.

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