I've been able to get over 40mpg doing 50-55mph with the cruise on in my GTP, just staying out of it is the best way to get good mileage. As for the shutting off the engine thing I have done it at lights where I know I'll be waiting a good 3-5 minutes or at DMV, other than that I'll let it idle...there are open loop tables in the pcm that will automatically richen the mixture upon startup for a set amount of time even if the engine is warm so depending on that mixture & how long its set to stay rich its usually not worth it for any short amount of time although I wouldn't be worried about starting your vehicle. If thats your main concern maybe you should ride a bike instead as they have no 'startup' issues...I dunno about you guys but I've started my gtp up probably 10-20 thousand times over the last 4 years I've owned it so starting it isn't much of an issue
