It's a little cold here, been around 1c and battery isn't liking that much.. It's certainly aging, and i'm now reluctant to engine off coast and all those techniques.
I cleaned my EGR not too long ago, and now the car consumes 0.12-0.15gal/hr at idle, which is nice.. So I keep the car idling unless i'm at a long stop, where i can turn off my headlights, turn down interior fan and all that stuff.
It'll cost a few mpg sure around town, but a new battery costs quite a bit. (I monitor battery voltage and my safe value is around 11.8-11.7v i start the engine at, it takes roughly 1min to drop to this value from charged if headlights are on!! (which are LED retrofits, 30w each) )
When it dies it dies, fortunately i live on a hill, could bump start it.
I did a 300 mile trip on Monday, the jazz is not designed for high speed driving and so I got 57mpg going between 55-70mph.. and 54mpg on the way back, 60-65(most of the time) and occasional 70 downhills.
At 70mph, it's doing 3500rpm!
roughly 45-48mpg at 70mph (all imperial gallons, not US).. Fit/jazz has aerodynamics of a brick.
I don't pulse and glide on the flat, but downhill I try to coast at idle, sometimes i let speed drop from 65 to 55mph..