1. My coolant is 2 years old. I was told to change and flush it every 2 years by my mechanic, does that sound right?

2. I read here at DTR that the "chevron/detroit ECL?" at 50/50 mix is the best coolant to use versus the dexcool.

3. I also heard there is an additive that comes in a tablet form or maybe liquid form that will help with the cooling system longevity? Not sure what it is called though.

 

More than you ever wanted to know> http://www.cummins.dk/fileadmin/doku...aintenance.htm

Personally I just use whatever brand of orange long life coolant my local Napa has on sale mixed 50/50 with distilled water. Just make sure it's low silicate for diesel engines. Most of it is.
I've been changing every five years.

 

That's a great read, very informing, but I'll probably stick to answer #2.

So just the low silicate at 50/50 with distilled water. Got it, thanks.

oh yeah, and make sure it's on sale.