I fill up my gas tank max full all the time, but I has notice the electronic dash board shown a various of different available miles each time I max fill the gas tank.
It used to shown it was at 409 miles before the tank is empty, now I'm only getting 350-380. Still driving the same condition as the normally drive.
What does your show when you max fill the tank?

 

It depends on what the Avg MPG was for the last 20 or so miles.

If it was all highway it would predict you have 400-500 mile till empty. If it was all city it may be predicting as low as 250 miles till empty.

 

Have just refilled this morning and got 1023 km to empty This car rocks!

Odometer was showing 837 km on 60 L diesel that's 7,1 L / 100 KM, as my boardcomputer said (I reset it when i fill it up)

The last part of the trip (499km) the Journey computer was showing 6,5L / 100 KM That's nice!

After another trip, see picture...

 

Well, I just schedule my BMW service appointment. I'm now only getting 321 miles before empty. This has concern me because I started to get 409, then 380, then 350 each time I max fill the tank.

 

As mentioned before it depends on your driving for the past several miles (I think it is more than 20). I frequently drive on the highway and it says over 500 miles. When I drive around town it is usually between 375 - 400. What you are getting seems very low.

 

If you want alot try clearing your Ave. MPG like right before you fill up. then it'll show like over 400 miles till empty. I think that works.