My wife and I have taken the exact same route (65% city and 35% highway) for the past year and a half in this vehicle.

The improvement was noticeable, like instantaneously.
I was able to tell a change/improvement right away - after I got our vehicle back from the dealership that day, but I held off in saying anything until I saw it continue/repeatedly hit those MPG numbers.

That's way I waited a whole week before I mentioned it here.

 

well, that's awesome. i wouldn't expect to get mpg's that good with the 2.4 and our 95% city driving. seems like 22-24mpg is where its usually at.

 

Fairly soon, I'm going to have to pull all my sparkplugs and check them out.
(I'm just praying the electrodes aren't covered in carbon crusties)
Knowing now that my alternator weren't spinning at full revs, it's likely to have caused those sparks to foul up due to lower voltages...

 

I also experienced this same issue with more warning lamps. Mine happened in very early October.

Got in it, tried to start it, made the clicking noise and a whole bunch of warning messages cycled. Service 4wd, Trans Overheat, ASC system service required, 4wd System Temp: Slow Down, and a few more. Finally, it got tired of displaying all of these messages and just went to SERVICE ELECTRICAL SYSTEM with a red X. Called Mitsubishi roadside, got a confirmation for a tow truck. He called me back because he wanted to make sure I was able to get the trans into neutral and I didn't have anything to pop the shifter interlock cover off, so I figured I'd see if the interlock solenoid still worked under its own power. The vehicle started with no problem. No check engine lights, like nothing ever happened. Mitsubishi couldn't find anything aside from a code stored that meant something along the lines of "Car could not communicate with CANBUS component". Battery and charging system were all fine, no dead cells or anything. Its not happened again, the dealer cleaned off the battery terminals in hopes of quelling any voltage surges or drops which can disturb components of the CANBUS system (they are very particular about voltages being precise and consistent).

 

hmm ... maybe i'll throw a "grounding kit" in. i did it to my G37 for about $20-$25 in parts. certainly can't hurt, and its cheap enough if you do it yourself.