BMW with DInantronics Tuner: MPG boost?
 

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?

I take it, that 93 octane premium was no ethanol? E0?

That's good going for a petrol engine, about a 16.5% increase V's the EPA highway figure, I wonder how you would have done in the diesel Xdrive? If you had exceeded the "highway" figure for it in the EU test by the same percentage, you would have got about 55 US Mpg, or 66 UK MPG. BMW has been developing the efficiency of thier engines alot recently, and it seems like it's paying off.

I had a tuning box fitted to my last car and the extra power helped th economy as the engine was needing less energy when being worked. I am considering having a new map put on and fitting it to my current car, just to see what a difference it makes.

From what I've read some 93 has ethanol and some doesn't, including Shell V-power which is what I used on those last two tanks of the trip. Maybe if I'd looked closely at the pump or asked...but I didn't, so I don't know is the short answer.

On the trip as a whole I had to settle for 91 on 3 of 8 fill ups, couldn't find 93 in northern Ontario or two fill ups in Minnesota. With the tuner you can feel the difference in acceleration with 93 v 91 as the increase in turbo boost is pushing on the knock limit, but I couldn't make a scientific finding if it affected the mileage.

E10 versus E0 should make a big difference in mileage.
My personal experience is 22% better with E0.
From what I've seen. Most Premium is E0.

Likely E10 in Pennsylvania. The E0 I can get without taking a 40 minute round trip is racing fuels sold by the jug or barrel at about $8 a gallon.

This site 'puregas' says around 3% which sounds correct. If the fuel is only 10% ethanol, hard to see how it could cause a 20%+ difference in mileage. It says E85 causes that kind of difference, which also makes sense.
about pure-gas.org

Also looking at their map it doesn't seem either of the ~40mpg fill ups were at stations selling E0.

Premium in Europe is a higher octane than in the US. The BMW engine might be able to take advantage of the boosted octane of the E10 premium.

Europe measures the octane differently than North America with the same fuel showing a 4 - 6 lower octane at the pumps if measured the way North America rates fuel. I normally use Chevron 94 Octane non ethanol which is app equal to 99 Octane if measured in Europe.

Of course some American states do sell crap On a trip passing through Montana in one town the Shell station had 86 octane and the best was 89 octane all with 10%

https://en.wikipedia.org/wiki/Octane_rating

Difference between RON, MON, and AKI

Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's Sensitivity,[

I am aware of the difference, and 99 RON is slightly higher than the 93 AKI we get for premium. It is enough difference than mixing in 10% ethanol to US premium will cover it.

RON is a better metric on how the fuel will behave in a modern, fuel injected engine. AKI and MON are holdovers from when there was still carbureted cars being sold. The auot manufacturers would welcome the US going to RON.

You were likely at high elevation where you were in Montana. The thinner air and lower pressures mean a naturally aspirated engine doesn't need as high of an octane.