I've owned a 2008 automatic xB for about a month. I average 29 mpg. I usually stop for gas when the gauge is about 1/8 tank. I usually put in about 9 gallons. The last time I filled up I drove it well past the time the gas light came on.
The range computer showed I could only go about 15 more miles. The tank would only take 11.3 gallons. Everything I've read shows the thank should hold 14 gallons, but, even with the tank nearly completely dry, I could put in less than 12.

Has anyone else had this problem??? Could Scion have put the wrong tank on my car!!??

 

If I am thinking to error on the side of safety.... I figgure that the Scion's "miles to go 'till empty" is probally a bit forgiving.. meaning that for example... if the computer says that you only have 15 more miles left, in all actually, you probally could go 25 miles before you really run out!.. Just a guess, All I am saying...
BUT... I have an experiment for you........ since it's still new I feel you could pull this off without suffering any ill side effects....
Get yourself a gas can with say 2 gallons in it & put in in the back of your xB2 along with a funnel...
NOW.. next time you run LOW on fuel, go ahead & keep driving. keep driving till you run her completely out!!! Till she stalls!!! (all the while with your "Miles 2 MT" light on).
Then put your 2 gallons in & start her up & drive it to the gas station & fill her up!. Let's see how many gallons it will take to fill it up!!!
Try that & let us know just how far you drove when the computer said you couldn't & how much gas it takes to fill it after completly empting her out!... Good Luck .. jh

 

danny53012, here are some earlier threads on this topic you might be interested in reading:
https://www.scionlife.com/forums/viewtopic.php?t=182226 Fuel gauge calibration (guage is off)
https://www.scionlife.com/forums/viewtopic.php?t=183830 12 or 14 Gallon Tank?

As for the proposed experiment, please don't let me stop you from running the experiment, as I too would be curious how many gallons you'd actually get. (But not curious enough to do it myself ) I know from my own gas receipts that the tank holds at least 12.8 gallons.

Has anyone put in more than 12.8 gallons in the tank?

 

If you're an Autoclub member, i'm sure they'd understand when they come and have to give you a gallon or two out in the middle of nowhere.

~They ask~
"didn't you understand the warning when you were running low on gas?"

~and you reply~
"Yea... I really didn't trust those Toyota engineers... you know they use metric, right?"