This weekend I drained the radiator of old fluid,poured a couple of gallons of water thru it while it wasn't running until it came out clean,then re-filled using 50/50 mix of green anti-freeze.Now when driving the temperature guage jumps from below 80 to 90-but never goes higher than that.It won't stay in one position anymore;before it was rock-steady at 90 after warm-up.After reading the posts,some guys say don't use green fluid-others say it's ok.Any thoughts on why this is happening?By the way-the old stuff seemed to be a mixture of green and orange.....