Is Dex-cool still a mess? Prestone Dex-cool? Is Prestone or some other 50/50 a better choice? Its funny how time flies. Except for my Deere I don’t think I’ve messed around with antifreeze for 20 years.
I'm in the northeast, and I use a Prestone premix but I like John's 30/70 mix idea. Because of snow and salt I seldom drive much in the winter, I wait until a good rain has washed a lot of salt/sand off the roads and only shoot for an hours ride once a month or whatever works. Here in western mass the temps can get down to single digits quite a bit. Some guys will tell you that running straight coolant could cause your motor to overheat, claiming it's a lot less effective at dissipating heat in the system.
A few years ago we had our own "slope" behind the garage. AWD and snowmobiles were one way to get around that week, no Camaro's LOL.
My go to would be Prestone but the reason I asked was primarily about gunk and corrosion. I remember when Zerex first came out and clogged radiators everywhere. As I recall Dexcool did the same and even wound up with multiple class action lawsuits. Between market forces and EPA involvement I was curious where coolant had evolved to but it appears Prestone is still the same.
"Honey... the old coolant has messed up the motor so much, I'm gonna have to yank it out and put in a new, blueprint engine with a warranty... and of course I'll use the newest, best coolant to protect the new motor".
When Dexcool came out in 96 its was intended to last for 100k mi when "major service" (plugs, wires, hoses, belts, etc) was dictated in the service schedule
Problem was GM also added "pellets" in the cooling system as leak preventative those pellets did react to the Dexcool and caused a brown milk shake sludge which quickly FU the cooling system. Without the pellets it was fine but was not worth the extra cost vs its use life
Dealership flushed my 96 within 18 months after buying it and put in green as the coolant was a milkshake with the Dexcool/stop leak pellet combo
IMHO store brand green and $1 gallon distilled H2O mixed to ratio that suits your climate
My math skills are rusty so I tried using the Google machine to see if they could give me a conversion chart LOL. No such luck. So typically, we have about 23-24 quarts of coolant in our BBC cars, and typically, we buy 50/50 premix stuff up here in New England. How much of my 50/50 coolant would I have to drain and replace with ionized/distilled water to get a 30/70 or a 40/60 mix? Starting with straight, undiluted coolant would make this simpler, but I'm not dumping 6 gallons of fresh coolant to experiment LOL. So calculating using the 50/50 that's in the car... what's the formula?
I came across this page "QUEST FOR THE IDEAL COOLANT" and the chart there suggests that a 70/30 mix would be OK down to 7° Fahrenheit and a 60/40 mix would be ok down to -10° Fahrenheit. Strangely, they suggest that the boiling point in either case would be 220° Fahrenheit. Based on the chart and article, here in Western New England they'd recommend the 40/60 mix or maybe a 35/65 mix if your car is safe in a garage that never hits 0°?
Check out the chart that Prestone prints on the bottle. A 40/60 Coolant/Water mix says its good to -12° Fahrenheit and the boil over protection is 260° Fahrenheit.
Adding water would raise the temp rating of the mixture and creating a weaker mixture that cant handle real cold days. So instead of -12F, it could be at or above 0F depending on amount of water added. Being in New England, you should prepare for power loss to the buildings for a day or two and no heat in garage for a prolonged time. I would add more straight coolant until you got enough to cover temps expected in the area for the winter plus 10 degrees. That is what my dad did for his 79 years of living in Maine. My 50 years of auto ownership, I have never needed any coolant rating value less than -15F and that was in North Georgia. Don't risk a block or heads thinking heat failure is a very remote possibility.
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