[BAKKI]

Flashed my stock 440i to BM3 stage 1 a week ago. Yesterday I made the 450mile drive from NorCal to SoCal -- a trip I make almost every month to visit family. Traffic conditions and median driving speed were same as usual as far as I could tell (~80mph on average, occasional light traffic).

- My historic fuel economy for this trip has consistently landed around 29 mpg (give or take 0.2).
- With BM3 I ended the trip with 31 mpg.

I will definitely repeat the experiment on the drive back, but for now I consider the almost +7% increase to be significant over the 450mile trip. I was optimistically hoping for highway MPG to stay around the same – so I'm very surprised to actually see an improvement in efficiency.

To my understanding, the tune runs a higher PSI than stock as well as a lower AFR (richer fuel mixture), which should lead to an increase in fuel usage. On the other hand, the power/torque increase across the band leads to less RPM needed to maintain a given speed, which should push down fuel usage. I assumed the two would somewhat cancel out, but perhaps the changes lead to a net improvement in fuel efficiency for a given amount of power. In other words, improved mpg post-flash given the same driving habits as before (obviously easier said than done).

Then again, I don't really know what I'm talking about and would love to hear others weigh in. Has anyone else experienced this? And if so, would this also apply to other performance mods, i.e. high-flow DP, stage 2, etc.?

[Jay5k]

You're not in boost when you're cruising on the highway. After replacing my spark plugs with NGK (gapped). I noticed my mpg went from 31 to 36 on longer trips (40+mi). Possibly the downpipe is more efficient too.

[BAKKI]

Jay5k wow that's huge. Which NGKs were they? And how many miles did your previous plugs have?

[FastF30]

I was getting 34mpg driving on last long trip.. stock plugs, MHD stage 2+ ...

[Jay5k]

Originally Posted by BAKKI

Jay5k wow that's huge. Which NGKs were they? And how many miles did your previous plugs have?

NGK 94201 gapped at 0.022. 40k miles on the old plugs.

[Ifellapart]

your tire pressure plays a big role as well.

[J555]

My Stage 1 93 increased the fuel consumption by approx. 10%. I think also the settings of exhaust aggressiveness/burbles affects that. Anyway, I don't mind

[mike@x-ph.com]

stage 1 does not change boost unless you're on wide-open throttle. If you drive the car more aggressively, it will consume more gas. If your driving habits are the same, fuel consumption is the same