I agree about checking the Civic. Whether it be auto mechanics or medical, the indicators for problems are not always the absolute values, but change. Some cars run normally in the higher ranges on a dial, that’s just calibration. If there are changes from this, as with dadoctah’s Civic, we have a problem. If it’s not a serious heating/cooling problem but the gauge itself, it’s as important to get it fixed. Stable is good.
I have an '00 Olds Silhouette (Chevy Venture/Ponitac Montana - its a GM 3.4L engine). When I got it I was disturbed by a fluctuating temp gauge. At idle it would slowly rise up until the fan kicked on & then it fell as it should.
I was disturbed b/c I’m accustomed to the steady temp reading I’ve always had on other cars & b/c this van had spent its life on DexCool & did have at least some cooling system sludge in it.
Anyway, I took an IR thermometer and went to work. I had 2 other cars for comparison - 1 Dodge Caravan & one Ford Escort.
What I learned is that the actual temp (measuring at the thermostat housing) worked almost exactly the same way in all three cars, fluctuating between about 200 - 240F. However, the only gauge that actually registered the fluctuation was the Silo’s gauge.
Way back when I was messing with this I had a thread on it: http://community.cartalk.com/discussion/2140995/normal-cooling-system-or-a-problem/p1
So anyway…long story short & echoing genex’s comment - I assume that the Escort & Caravan have heavily damped gauges, while the Silo does not. I was actually a little annoyed about this. I’d rather a temp gauge that gives me a reasonably accurate number. Of course, I’m also the type that wants my dashboard to be a scantool.
While I understand gauge damping, and I know that cars do vary, I believe that Uncle Turbo hit on the real reason cars’ temperatures don’t fluctuate as much as they used to. Emissions and CAFE requirements have driven designers to design engines and cooling systems to maintain the engine at its optimal temperature. Cooling systems many years ago were pretty crude, they simply kept the T-stat closed and flooded the engine with cold coolant when the T-stat opened. As long as the engine didn’t overheat, nobody cared. Today’s engines are designed to get to their optimum temperature ASAP and remain there. That’s where the best mileage and lowest emissions are.
In short, in the '50s the engine’s heat was just something to overcome. Today it’s a managed aspect of keeping emissions low and mileage high.