more MPG, now that is a dream, No engine size stated, (mine is 3.8L) there is one method, put a raw egg under the right foot, and never allow it to leak . The MPG (turned engine, brakes not dragging) is 100% related to ,car weight, and your happy right foot. less happy, more MPG. (i promise) there is no free lunch in Physics, heavy cars suck fuel. NO the chip deal. 1: hack in to the PCM. ( google for 3 days, you might find this. 2: then shut down closed loop ops (very illegal) but my answers are pure physics and ECU tuning. 3: then set the AFR to 13.5:1 full time (Dyno tuned.) $$$$$ no free lunch on any Dyno either. 4: now car is gutless and will not accel. fast and will be a lean burn engine. The engine makes best MPG that is not the same Air fuel ratio of the legal 14.7: 1 ratio. (EPA) called Stoch, clean burn. 5: defeat enrich mode. next. if you really want to learn, read this book, sure will cost you $15 but its all there. every steps. Greg Banish
http://www.amazon.com/Engine-Management-Advance-Greg-Banish-ebook/dp/B009K4B66O/ref=sr_1_1_bnp_1_kin?ie=UTF8&qid=1394636425&sr=8-1&keywords=EFI+tuning and last , here is one car that gets 84mpg note the extremes.
http://www.youtube.com/watch?v=9XUKOUbp_PA&feature=player_detailpage#t=0s not that most CHIP sellers , lie about HP gains. 20% and all that.and if they SELL MPG chips, more lies. get the promise in writtingand with full refund , if it fails... they wont do that.then there are the guys that sell you a $100 , 3cent resistorthat replaces the IAT. the closed loop system will bypass that, SEE the longtermfuel trim , hide your fibbing IAT? sure.if you fib enough, say go too hot? the Closed loop will end or the the ECU will goto limphome.if it goes to limphome, MPG goes HORRIBLE.if not the hot (fibbing)
IAT sensor will cause lean burning.a good way to burn exhaust valves and makes tons of NOX pollution.(you will fail the smog test)and the new ECU on your car (i have an 08 JK)will throw DTCs for too lean. all day long.so what is the value in that? i dont know.so DIYbuy your custom ECU and programming.are you running fuel sucking A/T trannY?i designed my own MPG gauge. (obd2)my JeepsDASH MPG,(stock) is long run average. useless to me.My gauge is real time. all the time. averaged for about 3 seconds.if im a good boy (retired tech) i get 25mpg. (driving normal its 19mpg) 3.8L V8, 60k miles.get rid of weightget rid of A/Tbuy a guage and learn how to drive all over again. lots of coasting , avoiding the usage of brakes (safely)and slow Acceleration. ( Stay in closed loop, (my gage has that) and mPG just happens.fix dragging brakes, on car, , bad caliper guides?on the stock gauge you must push reset over and over.to get real time readings, that are meaning full. a pain. and first learn what a CHIP is ( it means nada)Make them tell you what it really is, or just pass.If you work hard for the money. that is.