My family is a GM family. There have been a few exceptions to this. My Grandma's parents owned a Ford Model T, found out it was a piece of junk, and traded it for a Chevrolet. I owned a 1995 Ford Mustang GT for a few months back in 1997 (great car). And my brother currently owns a Mitsubishi Eclipse.
I am the one that usually changes the coolant in my family's vehicles. I remember back around 1996 or so, I was driving a 1985 Chevrolet Monte Carlo and decided to convert it to the new red DEX-COOL coolant that had just came out. When I say "convert" I mean doing my 22 steps below as to obtain a 60% antifreeze to 40% water mixture. I later bought a 1991 Chevrolet Lumina and then a 1992 Chevrolet S-10 after owning several other cars between those and the 1985 Chevrolet Monte Carlo. I converted the Lumina to DEX-COOL. It ruined a gasket that had to be replaced. The S-10 was even worse. After converting it, it would blow smoke out of the tailpipe every time it was started due to coolant leaking into one of the cylinders.
I decided to get rid of the S-10 earlier this month and bought a 1995 Pontiac Grand Prix GTP with every option imaginable. After a few days of owning it, I checked the coolant to find that it was BROWN! That means it hadn't been serviced for quite some time. I figured it was DEX-COOL so I flushed the cooling system and poured in some fresh DEX-COOL. After doing that, I found out it had conventional green instead so, after about 3 days of DEX-COOL, I converted my car back over to green using Zerex 5/100 Coolant. I think I got the DEX-COOL out in time before it could start eating away at gaskets and seals and start spawning that reddish brown mud in my cooling system.
Now around 2000, I converted my Mom's 1995 Chevrolet Monte Carlo from green to DEX-COOL. After finding out about my Pontiac originally having green, I decided to convert her car back to green. I was SHOCKED to find that the DEX-COOL had turned into that damned reddish brown mud. The throat of her radiator and the radiator cap were almost ruined. It took me an good hour of scrubbing the radiator cap with a tooth brush to get it clean.
I did the exact same thing to her car that I had done to mine. I used the back flush tee I had installed in 2000, back flushed her car with the engine running with the heater on high for 30 minutes, poured in a bottle of Zerex Super Cleaner, had her drive the car on and off for about 6 hours, drained the radiator, back flushed again with the engine on and the heater on high for 15 minutes (I was happy to see the mud coming out knowing the Zerex Super Cleaner had done its job), poured in a bottle of Zerex Super Flush and ran the engine for 15 minutes with the heater on high to be sure all the mud was gone, drained the radiator, hooked the hose back up to the back flushing tee, and back flushed again for 30 minutes. I drained the radiator, took out the overflow tank and cleaned it out with hot water, Dawn dish soap, and a bottle brush. I hooked the overflow tank back up, closed the radiator drain plug, put the cap back on the back flushing tee, and poured in Zerex
5/100 Coolant.That was about a 3 weeks ago. After checking the overflow tank, radiator, and radiator cap, I am happy to report that there is no mud and the car runs great.
All the above is my story with my experiences with DEX-COOL and conventional green coolant / antifreeze. I will now explain what I think of conventional green, DEX-COOL, and G-05.
DEX-COOL
I think this was a bad idea from the start. You would have to be a complete moron to run any coolant / antifreeze for 5 years. A lot of people also have the misunderstanding that they are not to touch it for 5 years. This is just stupidity created by GM.
I think the 2 biggest flaws to DEX-COOL are that if it gets into contact with conventional green directly or through the deposits left by conventional green, it will form that reddish brown mud. If DEX-COOL comes into contact with air either inside the cooling system or outside, it will form either the reddish brown mud or the red "cement". This has been proven by both owners of some 1996 - Present S-10s and owners of other GM vehicles.
I would probably recommend most folks stick with DEX-COOL if that is what their vehicle came with, but a lot of brave people have converted back to conventional green without any problems.
Conventional Green
I think it is the best especially for GM vehicles. If you do an extremely thorough back flush (the 22 steps listed below) you will get all the DEX-COOL out. I would HIGHLY recommend using Zerex 5/100 Coolant which most AutoZone stores carry.
G-05
I have not used this coolant yet, but keep hearing good things about it. It is designed to work in new Fords and Chryslers and has been used for many years by Mercedes and John Deere. I think GM will eventually switch to it.
Now if you would like to back flush the DEX-COOL or any other coolant out of your vehicle, do it this way (you are responsible for what you do to the vehicle you are working on).
1) Buy a few jugs of Zerex 5/100, either a Prestone or Zerex back flushing tee, a bottle of Zerex Super Cleaner, and a bottle of Zerex Super Flush. You might optionally want to go ahead and replace your thermostat.2) After driving the car for 30 minutes or longer, open the radiator drain c*ck, and let the radiator completely drain out. While you are waiting, find the heater core hose that runs into the engine (not the one going to the water pump) and cut it. Install your back flushing tee. Also disconnect your overflow tank hose.
3) After the radiator is drained, take off the radiator cap.4) Get your garden hose and screw it onto your back flushing tee connector then put the connector to the back flushing tee you installed..
5) Turn on the water and wait for water to start coming out of both the radiator drain and top radiator opening.6) Turn on your engine with your heater running on high and let the car back flush for 30 minutes.
7) Turn off the engine and disconnect your garden hose.8) Wait for the water to drain completely from the radiator.
9) Close the radiator drain c*ck.10) Pour in your bottle of Zerex Super Cleaner into the radiator.
11) Connect the overflow tank hose and top off radiator with water.12) If you have bleeder valves for air, turn the engine on with the valves open and wait for water to come out of them in a constant stream then close the valves.
13) Drive your vehicle for 4 - 6 hours which can be on and off and over a few days. Be careful the outside temperature is not 32° F or lower as water expands when it freezes which will ruin your radiator and your engine and other components.14) Repeat steps 1 - 12 except for step 10 pour in your bottle of Zerex Super Flush.
15) Run engine for 15 minutes.16) Repeat steps 1 - 9.
17) You may want to take out your overflow tank and scrub it inside and out with dish soap and a bottle brush. Be sure to rinse all the soap out of it. When you install it back into your vehicle, you may want to fill it up with water from your garden hose a few times and let it drain out through the disconnected overflow tank hose.18) Connect the overflow tank hose after the overflow tank has been rinsed and is completely empty.
19) Pour in your jugs of Zerex 5/100 Coolant slowly until the radiator is full of coolant. If it takes 1 1/2 jugs, then that is 6 quarts. If your system holds 12 quarts, then you have a 50/50 mixture.20) Fill the overflow tank with Zerex 5/100 Coolant until either the overflow tank is half full or you reach the HOT line.
21) Repeat step 12.22) That is pretty much it, but be sure to check your overflow tank and keep the coolant level at the COLD line after your vehicle has sat for 6 or
8 hours over the next few days and get into the habit of checking it at least once a week.Hopefully Helpful,
BTJustice