Mine's a 2005. The book says it's a 26.4 gallon (100 liters), but it also says Including Reserve Fuel "of about" 2.8 gallons (10.5 liters).
Some would look at that and think it's 26.4 gallons, and then there's another 2.8 gallon in reserve. They would be wrong. When the little orange triangle comes on, you're getting very close to the reserve fuel. Somewhere between the orange triangle and the bottom of the white mark at the E is when you are down to about 3 gallons, and when it's bottom of the white mark at E then you're on reserve fuel, about 2.8 gallons remaining.
But, when the orange triangle comes on, and where that needle is, depends on the orientation of the vehicle, where the triangle will light up prematurely and the needle will show very, very empty of you are driving uphill, and then the needle will settle back when on flat ground, and will move up a little if driving downhill. It can take several minutes of a stable orientation for the needle to move.
When there's about a needle's thickness of black space between the needle and the bottom of the white mark, you're right there in 26 gallon territory, give or take a half gallon (uphill, downhill, flat).
On mine, if it's smack dab in the middle between the two white marks at 1/2 full, I can just squeeze 15 gallons in there. Barely. If it's in the middle at the 1/4 tank mark, I can put 19.xxx gallons in there. It needs to be just a hair into the 1/4 tank mark for me to get 20 gallons in there.
Clearly, German Engineering wasn't applied to the accuracy of the fuel gauge. But it it consistent, and it doesn't take very long to figure out where you're at.
