BMW with DInantronics Tuner: MPG boost?

[Corry_El]

I just completed a 3510 mile road trip in my 2015 BMW 328i Xdrive (ie turbocharged 2 liter 4 cyl gasoline engine) right after installation of Dinantronics Stage 1 performance tuner, electronic waste gate version. Direct measurement of fuel and odometer (not trip computer) gave 38.25 mpg for the whole trip which included a bit of slow urban and very rural (even dirt road in some cases) driving but mainly two lane highways and Interstates. On the last two tanks of almost pure Interstate, flat terrain in IN/OH, mountainous in PA, 93 octane fuel, warm weather, cruise control at 65-70mph, BMW 'Eco Pro' mode setting, averaged slightly over 40 mpg. The car's EPA rating is 22/33.

The tuner is supposed to increase engine power, by 'fooling' the engine into thinking the turbo boost is less than it is, so making the ECU call for more, but is supposed to be more sophisticated than other tuners in smoothing out all the secondary effects (so BMW allows it without voiding the warranty). It definitely gives the car a kick (it was fun before to pass on two lane roads, now it's more fun). But it seems it might have boosted the mpg as well. This is the first trip of that length we've done with the car but the previous record pre tuner for a single tank was 38.3 mpg which as beaten 4 times on this trip.

Has anyone else tested (perhaps more scientifically) whether Dinantronics tuners improve BMW mileage?