Nando, I changed over to Evans NPG+ at 12,000 miles, currently have 42,000 miles. It is touted as being a true permanent antifreeze. The biggest drawback to using it is that you should purge your cooling system of all water. I removed and cleaned, dried my recovery tank. I drained my OE coolant and refilled with distilled water and an acidic cooling system cleaner (Prestone citric acid). Went on a ride of about 50 miles and drained that. Refilled with pure undiluted, no pre-mix Sierra coolant and repeated the ride and drain process. I then added 1/2 gallon of Evans NPG+ and rode again for a few miles before draining that. Then I refilled with the NPG+, replaced the recovery tank and have not looked back other than to inspect the system for leaks and to look into the radiator cap hole for tell-tale signs of corrosion or contaminated coolent -- all looks brand dew. I did have a seep from that lower triple fitting just above the cat. converter and the Evans product does stink pretty bad when it hits the exhaust. I got that fixed and no more leaks (knock on wood).
My bike never did puke when I would challenge it by riding at 15mph. It would peg and after an extended ride it would gurgle a bit when I stopped to let it idle cool, but never tossed its coolant upon the ground. Now, the needle is a good bit slower to actually peg, it rises quickly at first; I think even quicker than with water based coolant, but at about that last full notch below the red it is a very slow rise now. It will finally peg, but again it never boils over and does not even gurle when idle cooled.
What I "thnk" is happening is that the water based coolants are more efficient at removing BTUs from the engine up to a point, then as hot spots in the engine begin to make little steam pockets, say around passeges for the heads, the water based coolant becomes very inefficient due to steam, but the Evans NPG+ does not boil or steam so its efficiency holds steady and since the coolant gets even hotter the air to radiator temp difference is greater and even more BTUs are lost to the outside air. THe Evans product does not boil until it gets way hotter than the tolernace of water based products, so it keeps on protedting far longer and as it gets hotter it gets even more efficient due to the greater difference between the air temps and coolant temps.
So, under extreem conditions, does the NPG+ allow the engine to operate at a dangerously or damagingly high temp? NO. The engine temps will not become harmfully high until the collant boils and thus fails to keep the internal surfaces covered with liquid coolant. The water based products will allow steam pockets to from much sooner, and when it does the temps sky rocket to temps far the above boiling point of either product. So, technically, I believe pure water would be hard to beat for efficiency at "normal" operating temps, but very poor as we appriach even 212 degrees. 50:50 mix is more efficient then NPG+ until you get to about whatever its boiling point is under pressure; what is that, about 230 at most. NPG is less efficient at heat transfer up to that point, but keeps on protecting and won't boil over even at 300+ or some such. Steam from water based pockets allow engine temps to soar way above 300 very quickly -- no water, no steam. No water, no corrosion, no silicates either, NPG+ does not need them. No varnish-like coatings like the GM orange crap either.
So far, so good. I did not modify my system to run at low or no pressure. Evans says you can and for best cooling system service life you should, but leaving as is should be no disadvantage and the same wear and tear as the pressure system imparts with regular antifreeze. I do not worry about boil over or over heating.
We were riding two-up and heavy on the BRP last July. It was HOT. We visited Natural Bridge, VA, a fair detour from the BRP. Noticed a sign that read BRP 12 miles (as I recall). Neat, a short cut. THe black top stopped in less than a mile and it was very soft and deep freshly laid gravel and STEEP winding road. 1st gear, with medium throttle just to stay "afloat" on the soft gravel, about 15mph. Pegged that needle in less than half way and did not stop and did not worry. Finally hit the top and paused to listen to the rads, no gurgeling, no leaks, the heat for the engine/tranny case felt typical for any long ride, but the heat from the radiator and fans was very HOT. Pulled onto the BRP at 45 mph and the temp gague fell like a stone to its normal setting in less than one mile. Good stuff, no way would I have made that climb successfully with regular coolant and not boil over.
prs
