Zerex Z-05 is what I used in my IDI. I believe they have changed the formula recently, as it now has the Cummins spec number that is compatible with the older engines and seals. At one point in time it wasn't. It's not cheap thought.... expect $80+ for enough concentrate for an IDI. Next time I do a changed on the 6.0 I may used this in there, just to keep 1 coolant in stock.....
I just looked at the PI sheets for both:
G-05:
https://sharena21.springcm.com/Publ...2d889bd3/eac350d9-1c76-e711-9c10-ac162d889bd3
HD ELC:
https://sharena21.springcm.com/Publ...2d889bd3/5ba9e4a6-1c76-e711-9c10-ac162d889bd3
They are pretty similar in specs and such, except for:
1. G-05 is "low silicate" with around 300PPM; HD ELC doesn't mention silicate at all(I'm guessing it doesn't contain any?)
2. The two coolants meet *different* Navistar specs, no overlap. They both meet a number of other specs as well that do overlap.
3. The G-05 is slightly better in the "aluminum water pump cavitation test", both meet the ASTM spec.
4. There's a bunch of numbers in the various corrosion sample tests; both meet them all by a wide margin, but the numbers are different.
My guess at this point is they both will work fine, they both seem to have the same cost, they both are definitely different technologies(HD ELC when it evaporates leaves behind white/pink powder, I don't think the G-05 does that)... The silicate in the G-05 might have some additional protection properties, but might destroy water pump seals more than otherwise?
That's the best I can get out of them.