So, I just finished changing my oil at 25k miles. I was checking my other fluids and noticed that my coolant is really really low! As in, lower than the "low" line. I've never changed the coolant since I've had my car for the past 2 years. I've searched and read the existing threads.

I want to use Prestone 5/150 Extended Life Antifreeze which is silicate and phosphate free. So, I guess I have the OEM coolant in my car still.

For the record... Should I drain the remaining coolant out before using the Prestone? Or is it safe enough to just add it into the car?

You still have plenty of coolant even if the level in the bottle is below the line. At 25K you might as well drain what's in there and fill it up with new coolant. Be sure to follow the proper filling and bleeding procedure to avoid leaving any trapped air in the system.
To be sure you don't have any leaks, check around the upper radiator tank for signs of any seepage, also look at the upper and lower hoses to see if there is any leakage at their ends. With the system empty it's not a bad idea to pull the hoses off at the engine fittings and have a look- it's possible for small amounts of coolant to be leaking past the clamps and not be externally visible.
The Prestone coolant should be ok to use if it's silicate and phosphate free, however it can't be left in there for the 5/150 interval since it will be mixed with some of the remaining OEM coolant. Also before using, make sure the label indicates it can be mixed with conventional coolants.
You should take a look at this thread, the cooling system FAQ-
http://forums.nasioc.com/forums/showthread.php?s=&threadid=504002

What color coolant is in the car now? You shouldn't mix the different colors. Some colors are compatible with different one's, but just to reduce confusion you shouldn't mix them. If you want to run Prestone 5/150 Extended Life Antifreeze then why wouldn't you want to flush all the old out so you can replace it with what you want? Regardless, using phosphate and silicate-free coolant is what you need, as you mentioned above. Flushing the radiator is easy, flushing coolant (http://forums.nasioc.com/forums/showthread.php?s=&threadid=205802)

-Charles-

From everything I've read, coolant color is just that - color.

Not important. Whats important is the content.

From everything I've read, coolant color is just that - color. Not important. Whats important is the content.

Different contents evolve into different colors, and different contents/colors are not compatible.

just to reduce confusion you shouldn't mix them

If the coolant is green, don't add orange. I've seen people try to do this firsthand and the result was overheating. Flush everything thoroughly and add your Prestone Extended Life, which I think is orange, and you'll be fine.

-Charles-

Thanks you guys! Very helpful information. I guess I'll try to flush the existing coolant out tomorrow and add in my Prestone. Unless, there's something you guys want to add about which aftermarket brand would work better. Any suggestions? Thanks again. :)

As you can read in the Coolant FAQ thread, the Peak Global is considered safe to use in our cars. It is also an extended-life coolant but can be mixed with all types of OEM coolants, although the instructions specifically state that it must be replaced at the shorter intervals if mixed with standard stuff. I recently did my cooling system service and I used the Peak Global that comes in a 50/50 premix. This was very convenient, no mixing or worrying about using distilled water etc.
I am not familiar with the specs on the Prestone, but I will restate what I said above- if you plan to use it be sure it states that it is compatible with conventional antifreeze. If it is a Dexcool-type coolant I would not recommend using it. Even with a flush some of the original coolant will remain and may cause issues.

Originally posted by Mulder
As you can read in the Coolant FAQ thread, the Peak Global is considered safe to use in our cars. It is also an extended-life coolant but can be mixed with all types of OEM coolants, although the instructions specifically state that it must be replaced at the shorter intervals if mixed with standard stuff. I recently did my cooling system service and I used the Peak Global that comes in a 50/50 premix. This was very convenient, no mixing or worrying about using distilled water etc.
I am not familiar with the specs on the Prestone, but I will restate what I said above- if you plan to use it be sure it states that it is compatible with conventional antifreeze. If it is a Dexcool-type coolant I would not recommend using it. Even with a flush some of the original coolant will remain and may cause issues.

Hmm... Where can one find this Peak Global, assuming that's the brand. Can I find it at any local Autozone, Kragen, PepBoys?

Probably, most of the major stores should have it. "Peak" is the brand, "Global" is the type. Peak makes other types of coolant as well.

Thanks for the info Mulder.