Ok now comes the tricky question...... Green coolant ..or..Orange coolant..?  Or make that the psycodelic question.   What cools better in our situation?        David Cook  RV6A Rotary.

My advice is – stay away from the orange coolant.  I assume by orange you mean Dex-Cool or similar so-called “extended use” silicone based stuff.  I had it in my system for about 18 months.  I initially noticed that where some hot coolant from the overflow splashed onto the outside of the aluminum coolant lines it left an indelible stain.  That seemed weird, but I didn’t do anything about it.  After about 18 months of use I took out my wing-root radiator to work on the air ducting, and looking into the end tank I could see strange globs of yellow deposits around the edges of the tube entrances; enough the impede flow.  I took out my in-cowl rad for inspection, and found the same thing there.

I took the rads to a radiator shop; had them flushed, flow and pressure tested.  The deposits flushed out and all was fine, and worked great since – with E-G (yellow) coolant.

I use about 30% coolant and distilled water.  I don’t know what the deposits were, and neither did the guy at the rad shop; but his advice was not to use dex-cool.

Al G