Stock P5 with AT and roof rails removed.
I have found that this car is very weight sensitive. Driving by myself with no cargo, I can consistently get 30-32mpg, but on trips with cargo and passengers, I can only manage 26-28, even though it is mostly cruising.
Keeping the RPMs below 3500 accelerating is a must for good mpg. I have learned to let the great suspension and tires do their work by braking less on turns and off ramps. I used to accelerate, brake hard, and then accelerate going through ramps. Getting the foot off the gas and letting the car cruise when getting close to a red light or ramp makes a noticable difference. Every time you brake, you are wasting previous acceleration. (boom03)
Oh and not all gasoline, or even different fillups are the same. Some engines do run better with certain formulations.