mine does the same thing but only in the drive way cus i dont have hills haha. mine is messed up to cus it willdrop really fast and and then will floot around E and 1/4. but it is consistent. a good tank so far will be at 100 at 1/2 and then the gas light willl pop on when i have about 5 gal left so that will be like 300 miles. so if you check your mileage everytime u fill up you should get a good estimate on what ur gas gauge should be even if its on a hill