The float is usually at the front of the tank. If you're pointing downhill, the reading will go up, if you're pointing uphill, it will go down. I know for my 97 Civic the float must be at the front right side, because in a prolonged left hand turn (very long freeway transitions) the gauge will go up. On a prolonged right turn, the gas gauge goes down. The most accurate way to know is based on what it says your fuel economy is for that tank and how many miles since you filled up. Some quick math and that tells you how many gallons you've used.