article out of motor age magazine. found it in my shop 
bear with me throught the first bit, it gets interesting. I'll mark if you want to skip through the crap and get right to teh useful stuff.
CHANGING COOLANT TODAY [In some ways antifreeze has changed dramatically since we (or our parents) were kids. In some ways it hasn't changed at all. And in some ways, say some suppliers, it's changing back... Or is it?]
We're approaching the season when, in the mid 1950's - the "happy days" era - Milwaukee's Howard Cunningham would have had mechaninc Arthur Fonzarelli "winterize" his DeSoto. are you old enough to remember real winterizing? The car would get a once-over inspection, a tune up, snow tires mounted and an oil change from SAE30 to 20W (or possibly 10W if closer to Christmas) The cooling system also got a special service.
The Fonz would always at least check antifreeze concentration with his hydrometer and adjust, if needed. But because winter in Wisconsin has always been serious and because Mr.C was always conscientious, ever other year Fonzie would flush the system and install fresh antifreeze. They could choose from the so-called "permanent" ethylene glycol-based products offered by several reputable suppliers. all were suitable for virtually any car or light truck.
The word permanent didn't fool Howard. He knew you couldn't leave the stuff in forever. He remembered the temperature gauge in his dad's car, marked "alcohol boils" at just under 150 degrees farenheit, the boiling point for methanol (wood alcohol). It wasn't unusual for the methanol some still used as antifreeze in the 1930's to boil off - even during winter driving - robbing the engine of freeze protection. That's why ethylene glycol based antifreeze was developed in the late '20's. It was permanent in that it wouldn't stealthily boil off or otherwise loose freeze protection. But after a couple years' use, the corrosion-inhibiting properties of accompanying substances would give out and the coolant would need to be renewed.
By the mid-1970's, winterizing had changed. Howard's son Richard didn't need to change oil viscosity because he used SAE 10W-30 in his plymouth year round. He considered his radial-ply tires adequate for winter use, too. One thing stayed the same, however: Every two years, he would have fresh, ethylene glycol antifreeze installed. It was essentialy the same antifreeze that had gone into his dad's DeSoto, but nearly nobody bothered using hte word "permanent" anymore.
Fast forward to 1998. If, tow years previously, a balding Richard had stuck with Mopars or had bought a ford instead of his 1996 oldsmobile, it would be time to renew his coolant. But starting with 1996 models, the factory fill for General Motors (GM) was Dex-Cool, with a recommended five year/100,000 mile (later 150,000 mile) replacement interval.
MARK!!
Today, you can still buy antifreeze much like the products Howard and Richard used. It hasn't always been green - never had to be but usually is - and it's acquired the nickname "green". It's suitable for just about any car or light truck, provided it was built before 1996. That's when things started to get interesting.
Okay, they got interesting even before that. During the 1970s and '80s, aluminum became increasingly popular for engine castings and radiators. the change was made to save weight, a direct result of the entergy crises of the era. Corrosion-inhibiting packages used in antifreeze had to change consequently because protection strategies that worked fine with cast iron and copper/brass weren't always right for aluminum.
[BOLD]SILICATE EVOLUTION[/B]
Temperatures near the exhaust valves in aluminum heads can get hot enough to boil away coolant - not necessarily from the entire system - just in pockets. The boiled off coolant can't go anywhere, it condenses back within the system; collant may ebb and flow in the area. Obviously, this has the potential to erode and otherwise damage the aluminum. In the 1970's, coolant chemists began adding silicates to help protect it.
Sometimes, silicate content was high enough that gelatinous blobs could drop out of suspension and clog the cooling system. In cars and light trucks, this wasn't likely unless someone topped off the system with too much straight antifreeze. In heavy-duty trucks, it could happen if someone got carried away charging the system.
By the 1990s, silicates had been made more stable and effective in smaller amounts; the dropout problem became less common though it may still occur in cases of silicate-overcharging. But when GM started using Dex-Cool as their factory fill wtih the '96 models, teh picture changed more radically.
BASIC COOLANT CHEMISTRY
Glycols aret he key ingredients in most antifreeze manufactured since about 1927. Propylene-glycol is appreciated by many, as it's less toxic than the more common ethylene-glycol
Mixing glycol with water lowers the freeze point of each. Plain ethylene-glycol freezes at 8 degrees farenheit. While plain water can actually carry heat away from an engine more effectively than a glycol/water mix, this mix has a higher boiling point than water alone, amking more-efficient operating temperatures possible while providing boil-over protection. Overheating is likely with more than 70 percent antifreeze in a cooling system.
The vast majority of coolant content is glycol/water. corrosion inhibitors only make up 2-5% of the mix, but they, and the dyes that are sometimes included, determine how the fluid is described.
Think you know something about antifreeze? So did I. But after two weeks of researching today's coolants one thing became evident: It's easy to get confused.
Here's one thing that's certain: There are three basic types of antifreeze available and in broad use today. They include traditional, green coolant; Dex-Cool, factory fill for GM since model year (MY) '96; and the Ford/Chrysler-spec fluid, also called G-05. Ford began using it in MY '01 and chrysler followed a year later.
We spoke with experts from four suppliers whose coolant products have been around, in one form or aonother, long enough that fonzie and Mr. C would have recongized theim. While there are other reputable antifreeze suppliers, the ones we consulted offer a cross section of the industry. Tow produce "universal" long-life coolants; one of these also makes Dex-Cool, while the ohter produces a G-05. Two offer GM-style Dex-Cool, as well as G-05. Each provided convincing reasons for offering their current lineup of products.
bear with me throught the first bit, it gets interesting. I'll mark if you want to skip through the crap and get right to teh useful stuff. CHANGING COOLANT TODAY [In some ways antifreeze has changed dramatically since we (or our parents) were kids. In some ways it hasn't changed at all. And in some ways, say some suppliers, it's changing back... Or is it?]
We're approaching the season when, in the mid 1950's - the "happy days" era - Milwaukee's Howard Cunningham would have had mechaninc Arthur Fonzarelli "winterize" his DeSoto. are you old enough to remember real winterizing? The car would get a once-over inspection, a tune up, snow tires mounted and an oil change from SAE30 to 20W (or possibly 10W if closer to Christmas) The cooling system also got a special service.
The Fonz would always at least check antifreeze concentration with his hydrometer and adjust, if needed. But because winter in Wisconsin has always been serious and because Mr.C was always conscientious, ever other year Fonzie would flush the system and install fresh antifreeze. They could choose from the so-called "permanent" ethylene glycol-based products offered by several reputable suppliers. all were suitable for virtually any car or light truck.
The word permanent didn't fool Howard. He knew you couldn't leave the stuff in forever. He remembered the temperature gauge in his dad's car, marked "alcohol boils" at just under 150 degrees farenheit, the boiling point for methanol (wood alcohol). It wasn't unusual for the methanol some still used as antifreeze in the 1930's to boil off - even during winter driving - robbing the engine of freeze protection. That's why ethylene glycol based antifreeze was developed in the late '20's. It was permanent in that it wouldn't stealthily boil off or otherwise loose freeze protection. But after a couple years' use, the corrosion-inhibiting properties of accompanying substances would give out and the coolant would need to be renewed.
By the mid-1970's, winterizing had changed. Howard's son Richard didn't need to change oil viscosity because he used SAE 10W-30 in his plymouth year round. He considered his radial-ply tires adequate for winter use, too. One thing stayed the same, however: Every two years, he would have fresh, ethylene glycol antifreeze installed. It was essentialy the same antifreeze that had gone into his dad's DeSoto, but nearly nobody bothered using hte word "permanent" anymore.
Fast forward to 1998. If, tow years previously, a balding Richard had stuck with Mopars or had bought a ford instead of his 1996 oldsmobile, it would be time to renew his coolant. But starting with 1996 models, the factory fill for General Motors (GM) was Dex-Cool, with a recommended five year/100,000 mile (later 150,000 mile) replacement interval.
MARK!!
Today, you can still buy antifreeze much like the products Howard and Richard used. It hasn't always been green - never had to be but usually is - and it's acquired the nickname "green". It's suitable for just about any car or light truck, provided it was built before 1996. That's when things started to get interesting.
Okay, they got interesting even before that. During the 1970s and '80s, aluminum became increasingly popular for engine castings and radiators. the change was made to save weight, a direct result of the entergy crises of the era. Corrosion-inhibiting packages used in antifreeze had to change consequently because protection strategies that worked fine with cast iron and copper/brass weren't always right for aluminum.
[BOLD]SILICATE EVOLUTION[/B]
Temperatures near the exhaust valves in aluminum heads can get hot enough to boil away coolant - not necessarily from the entire system - just in pockets. The boiled off coolant can't go anywhere, it condenses back within the system; collant may ebb and flow in the area. Obviously, this has the potential to erode and otherwise damage the aluminum. In the 1970's, coolant chemists began adding silicates to help protect it.
Sometimes, silicate content was high enough that gelatinous blobs could drop out of suspension and clog the cooling system. In cars and light trucks, this wasn't likely unless someone topped off the system with too much straight antifreeze. In heavy-duty trucks, it could happen if someone got carried away charging the system.
By the 1990s, silicates had been made more stable and effective in smaller amounts; the dropout problem became less common though it may still occur in cases of silicate-overcharging. But when GM started using Dex-Cool as their factory fill wtih the '96 models, teh picture changed more radically.
BASIC COOLANT CHEMISTRY
Glycols aret he key ingredients in most antifreeze manufactured since about 1927. Propylene-glycol is appreciated by many, as it's less toxic than the more common ethylene-glycol
Mixing glycol with water lowers the freeze point of each. Plain ethylene-glycol freezes at 8 degrees farenheit. While plain water can actually carry heat away from an engine more effectively than a glycol/water mix, this mix has a higher boiling point than water alone, amking more-efficient operating temperatures possible while providing boil-over protection. Overheating is likely with more than 70 percent antifreeze in a cooling system.
The vast majority of coolant content is glycol/water. corrosion inhibitors only make up 2-5% of the mix, but they, and the dyes that are sometimes included, determine how the fluid is described.
Think you know something about antifreeze? So did I. But after two weeks of researching today's coolants one thing became evident: It's easy to get confused.
Here's one thing that's certain: There are three basic types of antifreeze available and in broad use today. They include traditional, green coolant; Dex-Cool, factory fill for GM since model year (MY) '96; and the Ford/Chrysler-spec fluid, also called G-05. Ford began using it in MY '01 and chrysler followed a year later.
We spoke with experts from four suppliers whose coolant products have been around, in one form or aonother, long enough that fonzie and Mr. C would have recongized theim. While there are other reputable antifreeze suppliers, the ones we consulted offer a cross section of the industry. Tow produce "universal" long-life coolants; one of these also makes Dex-Cool, while the ohter produces a G-05. Two offer GM-style Dex-Cool, as well as G-05. Each provided convincing reasons for offering their current lineup of products.
