I purchased some Prestone long-life antifreeze (orange color) from Advance Auto Parts a month ago and used it to top off the coolant in my '68. The label said it was GM DexCool approved, and there was NO warning about it not being compatible with regular Prestone.

However, I've found several threads on Pennock's Fiero Forum (Dexcool Vs Ethylene glycol. (http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20020208-2-010818.html), New Aluminum Water Pump: Dex-cool?? (http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20020511-2-016712.html), and Can you mix Prestone 5/150 with Regular coolant? Green/Orange? (http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20021104-2-022978.html)) that relate horror stories about using this stuff. Do I need to flush the '68 or is it ok to have mixed the two?

Thanks in advance.

[This message has been edited by cturner (edited 01-27-2003).]

i don't think you are supposed to mix the stuff, and from what the GM dealer techs i know say, you should avoid the expensive Dexcool stuff like the plague. i have heard reports of it crystalizing in the radiators and heater cores and clogging things up really good.

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see dirty pics here of a car that gets driven http://community.webshots.com/user/novaderrik

I do not believe they are to be mixed. Although I've read the articles, my personal experience is OK. I have a 97 GMC that has had the stuff since new. Now 70K miles and not a hint of problems.

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Rick Dorion
69 RS Conv,355,Autogear M22,4.10's and I don't worry about stone chips ( yet ).

The DexCool stuff is different than the Prestone Extended Life stuff. GM has had all kinds of issues with Dex Cool, crytallizing, corroding heater cores and the like. I ran the stuff in my 96 GMC for 70,000 miles (about 3 years) before replacing it with the Prestone Extended Life Antifreeze and have never had any problems like people have described. I don't think GM is even making Dex-Cool anymore, they are using the Prestone stuff. The prestone antifreeze will not crystalize like the Dex cool will. It is also OK to mix it, but not really recommended. Apparently the resultant mix of coolants will turn brown, but it won't crytalize, or turn to jello or any other weird fluid. I ran the Prestone stuff in my Camaro last year and thought I really flushed out all the old green antifreeze really well, but I didn't get it all out apparently as my coolant turned a nasty brown color. It didn't affect the cooling capacity of the car, and I can see no deposits of any kind in the radiator.


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine (http://www.townisp.com/~markcanning/camaro/transparent%20air%20cleaner3.jpg)

Mixing the two will only negate (fancy word) the advantages of the extended life. When the two are mixed, it looks funny and and has the same affect as using the green stuff.