Nope. First, you know you drove it after the top off, just for kicks. So that probably burned some off. Second, some of it poured out on the road. And, third, you probably measured wrong. I know this because an old S-10 I had held 7 quarts but it said it only held five. I know that because the mechanic yelled at me about overfilling. And last, these days it probably evaporates faster given the climate change and acid rain factors.