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Registered
2006 CTS
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258 Posts
Discussion Starter #1
Haven't had a chance to pick up a Factory Service Manual yet, but I'm in a hurry to change the Trans Fluid and Filter and change the Engine Coolant on my '93 DeVille 4.9.

Just would like to check on any opinions out there on using my old favorite, Pennzoil Dexron/Mercon III in the trans,

and any opinions on using regular 'ol Prestone Anti-Freeze.

I also read in my owners manual about adding a GM 1825 M Supplement (Sealer) in the cooling system. Would you all recommend a supplement and if so, what would be a good aftermarket replacement additive?

Any info would be appreciated.
 

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Sedan de Ville, CTS
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4,764 Posts
No need for sealant unless you have a leak. Highly recommend tranny fluid change at each 25k. Do it yourself; do not use the automated flushing systems.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,990 Posts
DexronIII may be superceded by DexronVI now (or in the near future).
Conventional green prestone should be fine.
The GM sealant is the same as Barsleaks HDC (tabs) or G12BP (powdered).
 

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'87 SDV
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1,296 Posts
No need for sealant unless you have a leak. Highly recommend tranny fluid change at each 25k. Do it yourself; do not use the automated flushing systems.
You'll get varying opinions on the need for sealer (like z06bigbird's) but using it after you have a leak is too late. It's cheap insurance and recommended by the engineers who designed the 4.x. I would never run a 4.x engine without it, and change it myself every year. The GM tabs are about 6 bucks, Bars Leak Gold Seal is about $1.50 at WalMart.

The trans is a different matter. Check your owners manual maintenance schedule. Some techs believe that unless you're driving in mountains or pulling a trailer, changing trans fluid before 100k can cause more problems than it prevents.
 

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Cadillac Deville 1990
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266 Posts
The only comment I have is that pet safe coolant from Prestone. Cost the same and it may save a pets life...sorry but I am an animal lover...lol
 
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