K11 ones tend to be very odd. Apparantly something to do with the sender in the tank. Mine can say i have a quarter left but then go up to a third when I turn it on next time. I just drive it till the empty line and fill it up
mine kinda says its lower then it is when i switch on, then goes up abit, then starts coming back down again.... but yeah it also kinda has a mind of its own.
lots of quick acceleration also has the same effect...dont know how many times ive thought its been nearing empty only to find ive actually got a lot more than i thought.
The sensor is to the rear of the tank, you'll find that going uphill makes it seem like you have more fuel than you actually do, and going downhill has the opposite effect.