I use Evans Waterless Coolant in 6 of my 7 vehicles. In my 1984 & 85 M-B, the temperature gage might creep to 90 C, above the normal 82 C T-stat nominal under max thermal stress, which is climbing the I-5 South grade over the Tehachapi Mtns (to L.A.) on a 110 F day, driving uphill at 65 mph (redline at 120 C). The T-stat may still be controlling (not full open) since to open farther requires higher coolant temperature (engineers term "proportional droop"). Since the innards should never corrode, the cooling ability should never degrade, so "good enough". Ditto for my 2002 Chrysler T&C 3.8L minivan. Can't comment on my 3 old Mopars since haven't stressed them such yet.
My sole vehicle still on regular coolant is the 1996 Plymouth mininvan, and is instructive. I made the common mistake of refilling with "Extended life, 10 year" coolant ~6 years ago. I totally flushed it with house water (low minerals here) and ran a few days on straight water, flushing each time. But perhaps there was still some green coolant in the system since I later noticed brown particles floating at the top of the radiator for several years and finally overheating slightly when idling at long lights. A new flush and more green stuff (w/ distilled water) fixed that for a while, but returned a year later. In flushing, I got much more brownish stuff (nonmagnetic, but not gooky like oil) plus a lot of rust and iron particles (magnetic). I pulled out the radiator (pain in a minivan) and backflushed it upside down, catching the water. More brownish stuff came out, and even chunkier stuff when flushing the block (T-stat out). I'll install a new radiator (only $100) since it had possible rust streaks on the fins and not right anyway (a few bolt holes off, appeared warp, cheap on ebay perhaps factory reject). I recall the extended-life coolant was Autozone store brand and didn't say Dexcool (maybe just "for GM"), plus not sure I was aware of Death-cool at that time.
I noticed at the auto parts that normal green coolant says good for 2 years and even Dexcool now says only 5 years. That makes one-time Evans Coolant ($45/gal) more economical, especially if you value your time. It theoretically doesn't cool as well as 50/50 coolant, but if your vehicle doesn't overheat under worst conditions, it is fine and should stay that way. If cheap, you might roll-your-own since it is now 70% propylene glycol and 30% ethylene glycol (or vice-versa, check MSDS). You can buy the former as "pet-safe" Sierra coolant and the later is regular green coolant. But, most spec say "up to 5% water". You might boil the water off, as I did outdoors on a propane stove. Stay far from flammables since the vapors can catch fire, and have a steel pan to cover the pot and extinguish. Boiling point is high (400 F?) so when the coolant starts boiling, you can be pretty sure most trace water has already boiled away. I stuck paper in the vapors and it caught fire (propylene I recall). In another pass (ethylene I recall), it caught fire and burned violently, overflowing the pot onto the propane burner until I go the steel cover on. Not-advised and watch constantly if you do, but much effort to save maybe half price over just buying Evans.
