MB recommends a a mix of 55% antifreeze and 45% water. This will provide the best freeze protection (to -50 degrees F.) and boil over (to +268 degrees F.). Recall water freezes at 32 and boils over at 212. The 5% difference in mix does yield better protection without sacrificing the cooling effect of the water. Ken is correct, water transfers heat better than pure antifreeze and all manufacturers recommend mixing water with antifreeze. Antifreeze prevents corrosion/rust/cavitation. Water pumps use a seal to protect the bearings from the antifreeze/water mixture and some antifreeze manuf. claim their product lubricates this seal to prevent leakage.
Some of the new antifreezes made by Zerex and Texaco can last up to 5 years and 100,000 miles - look at the labels to find them. The older formulations should be changed every 2 years or 24,000 miles.
Your owners manual should have the info about the capacity of your cooling system. The table of contents or index will tell you where to look.
Hope this helps.
America: Land of the Free!
1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
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Last edited by tcane; 09-22-2001 at 12:35 AM.