changing coolant on 2007 2500HD

. . .Silica fallout is usually found in OLD antifreeze( REALLY OLD!!! ) & usually in Diesel engines IF not keeping up with their nitrate levels/ coolant filters. . . NOT an issue with todays coolants as they are formulated (When is last time in last 10 years anyone saw silicate fallout?). . .I worked a successful automotive cooling system shop (33 years) & yes, actually purchased FULL trailer loads (20 pallets) of coolant at a time. . .Only took a few classes on coolants & such but had 43 years in cooling systems industry addressing & solving problems with cooling systems. . .Also talked to several AC Delco guys(at trade shows) about their Dex-Cool problems & every one of them had a different answer. . .By the way your link did not work.. . .YMMV. . .

I did test it and its good to -34 but I am even more dis-satisfied that I got a slight bit of red left in my overfill tank and the rest of its greenish yellow. I am just in the bind whether to hope its fine, or bite the bullet and put back in some dex cool

#1Flyboy wrote:
. . .My questions would be how much was drained out and/or was it truly "flushed" out; how much 100% antifreeze went back in to bring the % solution up to where it should be & did anyone think of also adding a can of anti-rust? (I'd recommend you check your % solution of antifreeze with a refractometer ) All antifreezes are compatible (yes you can mix red, yellow, green & orange & no harm is done; the claim being you get the least amount of corrosion protection of the lowest protection antifreeze)( If you doubt my words PLEASE provide expert published opinion )Dex-Cool has been especially hard on 4 & 6 cyl GM engines but appears to do OK in 8 cyl gas & diesel motors. . .Me, on my 6.6 diesel, & believing Dex-Cool was GREAT for business but not for my vehicles, I high pressure reverse flushed out the Dex-Cool at 52K miles & put in 70% solution of 5 year / 150K mile long life ( Off brand but made by Prestone ) added a can of anti-rust & a bottle of diesel additive.. . Did it again at 100K. . But changed both T-Stats this time. . .Just my humble opinion; please no yelling or rants - don't want to spill my drink. . .Also did all my friends GM vehicles (all have trucks) at 50K miles Everybody is happy. . .

Although color has nothing to do with anti-freeze type or performance, they are not all compatible. I've taken some anti-freeze classes from Staveley to learn the differences between OAT and older typical Ethylene glycol coolants. The type of film and way the film is formed that protects the metals that interact with the coolant are different and you can have serious issues, one of the most serious being Silica fallout. There's a reason why even Valvoline puts this little disclaims in their FAQ section on their antifreeze website:

"Can you mix Dexcool® with other antifreeze products? Link
Improper mixing of coolants has the potential to cause corrosion issues. Valvoline recommends using the correct antifreeze/coolant for your particular application."

. . .My questions would be how much was drained out and/or was it truly "flushed" out; how much 100% antifreeze went back in to bring the % solution up to where it should be & did anyone think of also adding a can of anti-rust? (I'd recommend you check your % solution of antifreeze with a refractometer ) All antifreezes are compatible (yes you can mix red, yellow, green & orange & no harm is done; the claim being you get the least amount of corrosion protection of the lowest protection antifreeze)( If you doubt my words PLEASE provide expert published opinion )Dex-Cool has been especially hard on 4 & 6 cyl GM engines but appears to do OK in 8 cyl gas & diesel motors. . .Me, on my 6.6 diesel, & believing Dex-Cool was GREAT for business but not for my vehicles, I high pressure reverse flushed out the Dex-Cool at 52K miles & put in 70% solution of 5 year / 150K mile long life ( Off brand but made by Prestone ) added a can of anti-rust & a bottle of diesel additive.. . Did it again at 100K. . But changed both T-Stats this time. . .Just my humble opinion; please no yelling or rants - don't want to spill my drink. . .Also did all my friends GM vehicles (all have trucks) at 50K miles Everybody is happy. . .

GM should be putting out some sort of numerical standard that they have to meet in order for coolant to be compatible. I believe DEX-COOL is a pure OAT style coolant. You really don't want any incompatibility between coolants and I never trusted "Universal" coolants. The main problem with mixing incompatible coolants is getting some form of fallout, namely silica type fallout. This stuff then goes on to clog coolant passages and reduce cooling effectiveness.

Sadly, the coolant market has never been fully standardized like oil. All the car manufacturers have their own standards and color doesn't really mean much in the coolant world either.

I also decided to take a look at the website FAQ for valvoline and they really don't give an answer: "Can you mix Dexcool® with other antifreeze products?
Improper mixing of coolants has the potential to cause corrosion issues. Valvoline recommends using the correct antifreeze/coolant for your particular application."

I personally would dump the coolant if even the website doesn't give an actual answer. I just don't understand why they wouldn't carry the ZEREX Dexcool coolant, since that is dex-cool approved and made by Valvoline.

I'm also almost in the same boat. I want to get some spare anti-freeze to keep in the garage but Mopar went to an all new coolant formulation that has nothing like it on any store shelves. So the current "Grape Juice" coolant costs about 20 bucks a gallon pre-mixed. Waiting for a coolant to come out with a chrysler "MS" standard that matches the coolant. Also, it has been posted never to mix the new "Grape Juice" with the "Orange" coolant that's roughly the same as Dex-cool.

As long as the Spec #s correlate you can use it. Duramax-Chevy don't require, only recommend theirs. I use Caterpillar and you never drain it. At 300,000 miles you add a bottle of additive and go on. $17/gal. Delo has a 75,000 mile life with no additives.

Here's my take on this and it's only my take.

#1. Dexcool it a good coolant. (IMHO)

#2. You don't ever want to let Dexcool exposed to O2 or it will turn into a bad coolant REAL fast.

#3. You don't ever want to mix Dexcool and green.

#4. If you mix Dexcool and green you will get a milkshake of mud in your cooling system.

#5. If you want to change from Dexcool to green you need to really flush the system to make sure there is no more Dexcool left in the system.

#6. If you accidently mix Dexcool with green get that stuff out of your cooling system immediately!!!

And now I will let the people say if any gasket looks at Dexcool it will fail within 2.3 seconds. :B

I can't really say it will or won't hurt anything. That said, I would have taken my truck and money elsewhere. Most every manufacturer today has their own mix. There's no way for the average owner to know if it really matters.

Mark

mine says 150,000 or 5 years whichever comes first...

This is a pure WAG but I think GM really wants that orange stuff. Interestly, my owners manual shows change interval at 150K for regular driving.