So today it was about 104 degrees out and I was taking a little trip
in the '04 MSM. Everything was in the green, until I got off the
freeway after an 80mph or so sprint with traffic. I get stopped at the
light at the end of the ramp, get the green, and start to pull around
the corner...I look down, and the temp gauge is higher than it usually
is(!)

Normally, the temp gauge rides right about vertical on this miata. In
this instance, which happens to be the only time I've ever seen it
deviate from that spot, the edge of the needle cleared the 'barbs' on
the thermometer icon on the gauge.

So I got up to 45mph or so and shut the AC off, and within 10 seconds
the gauge went back down to where it normally sits, and it stayed
there the rest of the way home. I turned the AC back on after a minute
or so and saw no difference.

Coolant level is full, no leaks. Engine was running fine the whole
time. It was a bit unnerving though. When I changed the coolant a few
months ago I cut the coolant 50/50 with distilled water, and now I'm
thinking I should maybe run it a little leaner than that and go maybe
70/30 instead. What's the general consensus out there? I'm in Phoenix,
it doesn't get very cold here. I guess I could drain out a quart or so
from the bottom and then top the system off with distilled to get me a
leaner mix in the system......if it would help.

Thanks,