Peak? Zerex? Prestone? Any suggestions what to use or avoid. 31,0000 troublefree miles so far....thanx

They're all just fine, but don't mix the "long life" coolant with the regular kind you already have. I'm not even 100% sure the long life type would be suitable even if all the old coolant were fully removed. There are some issues with some of the long-life coolants and certain types of engine parts, not sure if the X engine will tolerate it. Probably would, but FYI.

Brent

leftydog,
Just to add something from my Honda experience...
Honda's seem not to like any coolant with silicates, borates or phosphates. And that's what Honda specifies for their coolant. Not wanting to pay $18 for premixed coolant, I did some research and found that Zerex Extended Life is ok for Honda cooling systems because it is free from the above particulates. So I'd think it would be ok for the Nissan, but I haven't researched it yet.
From what I understand, it's the regular old prestone with it's phosphate rich formula that attacks the soft metals over time. This isn't really an issue with a cast iron block and head, but when you get into alloys...hmm.
As far as mixing the two types, I don't see a problem. They are both ethelyne glycol based. I went to NAPA to pick up a few gallons of the Zerex and the counter guy cautioned me NEVER to mix the two, implying something just shy of a vortex to hell would open if I did. I asked why and he said the extended life stuff isn't made from ethylene glycol. So, I had to show him where it stated just the opposite on the container... :rolleyes:
In any case, get as much of the old stuff out as you can out of there using the Nissan directions as rb42 mentions and make sure you use distilled water. Unless you have extremely soft tap water, don't let it come near your cooling system. Additionally, you should perform this service once every two years.
One other note. What you're looking for with modern vehicles is something that won't attack soft metal, hence the silicate, borate and phosphate free requirement. When you go shopping for some coolant, the parts people will often ask what color you want...whic in this case is actually irrelevant as some Dexcool type stuff does have silicates. Regardless of how "long life" the stuff is, I'd still change it every two years. This stuff does break down over time and become more acidic...
Bogatyr

31K might be a little early for the first coolant change; I think it's due at 60K for the first, 30K after. Unless you're a total cheapskate, buy the coolant from the dealer. For the $23 difference it's not worth the worry. Coolants are getting complicated these days, but they have longer service intervals.

It says "Nissan Longlife Antfreeze/Coolant" on the container, and "no amines, no silicates, ...no borates..."

Thanx for the advice. I have bought regular prestone AF, but will wait till next year to change it. And since I just bought an odyssey I especially value the Honda advice....Sorry...but can't see paying Nissan price for antifreeze...I use all synthetics now (transfer case, diff fluid, ATF, power steering fluid)...so I prefer to choose 3rd party stuff if I can. What is the coolant capacity for the V6 SC engine? How much Prestone do I add and how much water should I mix it with....thanx

30k miles is a good time for coolant service(every 2 years or earlier). Waiting longer will cause problems AFTER the warranty expires.

Genuine Nissan antifreeze isn't too expensive. Flushing is not needed. Drain/refill radiator with a 50:50 premix(this is very cheap and yearly service will prevent cooling problems).

DON'T USE DEXCOOL. I hope that you got Prestone in the yellow bottle.