I'm taking my truck in for bullet proofing and my mechanic shied away from the idea of CAT ELC. He said his buddy who works for CAT told him the coolant system needs to be sterile of all debris
I'm not sure that this state can be achieved, and certainly not maintained. Sand coming out of the casting is one factor, mould release agents on the interior of the hoses, plasticizers leaching -- lots of others. Of course it's best to run the ELC in a new system, but not everyone wants to buy a new truck to run improved coolant in.
or the CAT ELC's longevity will significantly decrease.
From 750,000 miles/12,000 hours/8 years to what? 500,000 miles/8,000hours/5 years? That would be a "significant" reduction to many people. Is the service life reduced below 50,000 miles/800 hours/1-2 years where the Gold is? I would be astonished.
Standard flushing procedures aren't good enough to reach the full benefit.
No doubt. However, the second or third-hand claims are not quantitative and I would not give them "significant" weight. If someone said that their results supported a reduction of 20% in coolant service life on a converted system, for example, that would be more credible. If they said 50% reduction, it might raise some eyebrows and elicit more questions, but it could be a useful datum.
Should I say I still want the CAT ELC or go with the idea of the gold coolant and just flush it more often and go with a coolant filter?
I see no advantage to running Gold, nor any reason to think that a "reduced" service life from ELC is a significant disadvantage. Delo ELC costs less for me locally than any G-05 coolant.
My opinion is that the EC-1 coolants are superior to the Gold, will last longer and cause fewer problems. Regardless of what the manufacturer might claim, I wouldn't put it in and then forget about it; nor would I necessarily follow the currently recommended flush interval for the Gold. On the initial ELC fill switching from Gold, a prudent person might do the 50k mile drain/refill once to clear the residual coatings which are replaced at the surfaces over time, and then take it from there. My experience has always been that things break or otherwise go wrong; I also have a history of mucking with things to try to make them better, and will probably break into any given system at some point whether it's a repair, upgrade, or maintenance. Personally, I've never been able to run the same coolant longer than 4-5 years or 100k miles due to these factors, and anytime it's drained would probably replace it anyway. If the repairs don't come and the upgrade bug doesn't bite, then I would base coolant maintenance intervals on chemical analysis, as many do with engine oil. IMO it would be a major miracle to make 750k miles without having had a good opportunity to replace the coolant. On the other hand, it would be foolish to not plan on replacing G-05 every 50k.