I always thought the modern larger 4.2 supercharged would be better than the 3.0 because for a given driving experience (driven conservatively), it would use lthe same or less fuel. The larger unit is less stressed so should last longer. My problem is keeping away from the tendancy to 'light her up' at every opportunity! Without traffic the STR looks like it will get 26 mpg (US gall); however commuting involves other people and a lack of understanding about keeping a working distance between vehicles. Here in chicagoland a car and a halfs length is not attainable! Oh for German regulations that enforce vehicle distance!

It's all about "power to weight". A powerful car driven gently will get better mileage then a low powered car driven hard to keep up.

Here is the best example I can think of.

Top Gear: The one gallon race. - YouTube

Thanks JagV8 for the link in post#37.
Another thing I had been looking for to see my actual coolant or head temp.Engineering Test Mode – Message CenterTo enter the instrument cluster Self-Diagnostic Mode:

1. simultaneously press and hold the trip meter reset button and
2. turn the ignition switch to position II
3. When TEST is displayed in the LCD, release the button.

The instrument cluster will enter the gauge sweep test. To navigate through the Self-Diagnostic Mode tests

1. press the trip meter RESET button repeatedly as required.

The self-test is deactivated when the ignition switch is turned to the OFF position or when the tripmeter reset button is pressed and held for 5 seconds.

Just be sure to ignore the weird codes in ETM as they will be years out of date.