I've been a member of the M5 forum since July of 2005, but did not get an M5 until June 
of 2010.  It's a Sport with the 5 speed automatic

I've posted in several other areas of the M5 forums, have a couple of posts in this MPG 
thread back in 2010 just after I got the car, but have refrained from more posts since I 
don't have that many miles on my car…just broke 14,000 at the end of July, 2013.  So, 
just over 4,500 miles a year so far.  Some years I put more miles on my road bicycles 
than on this car!  

My running average gas mileage has been in the mid-24 mpg area, the driving has 
consisted mainly of 'commuting' about 5 miles to 'town' 2-4 days a week to visit my 
clients (I'm a 'computer guy'), and some ~200 mile R/T drives to go bike riding in other 
areas in Oregon.

Anyway, at the end of July, I finally took a 'long' road trip, a total of 785 miles R/T up to 
the San Juan Islands in NW Washington State to do 4 days of bike riding on those 
islands.

I left Newport, Oregon, went up the coast, then inland to Portland, got on I-5 and drove 
up to Anacortes, WA, where we caught a ferry over to San Juan Island.

I filled up in Newport, drove north and got the 1st tank of gas in the Olympia, WA area, a 
distance of 242 miles, took 7.99 gallons for a tank average of 30.29 mpg.  This was with 
2 road bikes on a Yakima roof rack, 3 people in the car with a small amount of gear.  I 
used the cruise control when possible, and since it was warm (compared to the Oregon 
coast), I used the A/C as needed.  About half of this tank was on 2 lane 'rural' type 
roads, some limited stop and go in small towns, and then about 110 miles of I-5 driving 
at 60-70 mph.  Oh…and some very slow going, 'stop and go' on the freeway in several 
areas south of Olympia.

Some things I do to hopefully maximize the mileage is to NOT use the C/C on steeper 
hills to avoid it 'over-down-shifting' and to turn off the A/C on hills, back on on the flats.

That fill-up got me up to Anacortes, then back to the Olympia area, a total of 288 miles, 
where I put in 10.6 gallons.  Since it was a pre-pay cash fill, it might not have been 
totally full, but was close.  This worked out to 27 mpg.  It was much cooler coming back, 
and it was raining for quite a bit of the I-5 portion, and some lower speed driving around 
Anacortes before heading back.

From Olympia, it was straight down I-5 again, with only some minor slow-downs in 
places south of Tacoma, and in Portland.  This tank got me to with-in 50 miles of home, 
a run of 210 miles, used 6.676 gallons for 31.42 mpg.  Again, this was with 2 bikes on 
the roof rack, 3 people in the car and some light gear, a more limited use of the A/C 
since it was cooler and raining north of the SeaTac area.

So…the 'total' mpg for this trip worked out to 29.23.  I have gotten a few 28-30 mpg 
tanks before, but never for a trip of this distance.

My current running mpg since I got the car is right at 24.5 for the 14,000 miles.  Another 
thing I do when driving locally is to put the transmission in neutral when I'm stopped at a 
stop light that I know is going to be red for awhile to save the gas that would be wasted 
while idling in 'Drive' with the brakes on to stop the car from creeping forward.  I think 
this helps with my local mpg.

That's my story, and I'm sticking to it.