ANY ANTI FREEZE needs to be replaced every 3-5 years or so or at 150K miles which ever occurs first, and the RADIATOR FLUSHED of the crud that tends to accumulate, too keep it free of the stuff that tends to settle out and clog the passages. and too prevent the water / coolant mix from breaking down and acting like an electrolyte in a battery.
adding an ANODE or two can help.http://www.radiator.com/article-radiator-problems.htmlhttp://www.radiatorinfo.com/radtip.htmlhttp://forum.grumpysperformance.com/viewtopic.php?f=57&t=74http://www.ehow.com/how_2189727_prevent-clogged-radiator.htmlhttp://automechanics.wordpress.com/2008/05/28/top-ten-common-radiator-problems-for-older-vehicles/http://www.circletrack.com/enginetech/c ... index.html the ORANGE and GREEN anti-freeze most of us use are sometimes NOT compatible and if blended ,
IF mixed they frequently over time form a sludge, or break down and leave crud in the radiator passages that clogs the passages, THEY SHOULD NEVER BE MIXED adding an ANODE tends to slow the Corrosion, and having a good engine ground also tends to prevent or at least delay freeze plug and radiator corrosion problems running just water in a radiator allows it to act like the acid in a battery if your running aluminum parts like water pumps,radiators and heads on an iron block.
NEVER MIX
DEXCOOL
(ORANGE)AND PRESTONE
(GREEN)DON,T PLAY WELL TOGETHER
read thru the linkshttp://www.aa1car.com/library/2005/us90554.htmhttp://www.radiator.com/article-radiator-coolant.htmlhttp://www.aa1car.com/library/2004/us120426.htmif your finding a slime in the coolant passages of your aluminum intake on your engine, or your loosing freeze plugs (leaks) regularly its likely the result of electrolysis
heres one option that eliminates electrolysis
http://www.evanscooling.com/products/the cure requires three different changes, made to the coolant system,
the first is running a 50%/50% distilled water antifreeze mix with the newer antifreeze formulas
many guys clean the coolant passages in the manifolds and paint them with several coats of marine hull paint before installing them on a car also
the second is INSTALLING A COUPLE ANODES in the engine
the third is making sure the engines well grounded in two places to the BLOCK, not the intake, and to the cars frame and battery
http://www.flex-a-lite.com/auto/html/anode.htmlhttp://www.bmcno.org/RadCap.htm

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=74&p=4123&hilit=anode#p4123