Thanks again for the info Kent - great subject matter.

Short background: a few months back, I had a shiny new Peninsular engine installed at a Cummins shop that specializes in motorhomes. I told the guy several times, both in writing and verbally that I wanted him to fill the cooling system with Texaco Extended Life Prediluted 50/50 Coolant/Anti-Freeze ONLY. When I went to pick it up, I noticed a slight leak at one of the heater hoses - and noticed green a/f. I asked him if he had done what I told him to and he told me "hell no, the plain ole a/f is as good as any other kind, as long as you change it once in awhile". And, he mixed it with plain tap water! AARRRRGGGGGHHH!

So, I've got two choices: 1) try to remove whatever a/f is in there right now (and I'm not so sure how I'm going to get it all out), OR 2) make sure I keep the chemistry in good shape. I never got a good answer out of the guy about the brand of a/f he used and I'd guess it was the cheapest stuff he could find.

Question: if I can find a test kit and some Pennray/Nacool additive, do you think I can compensate for the tap water and green "brand x" a/f and just leave good enough alone? Sure would save a mess and omit the possibility of mixing two incompatible coolants.