I ride a vehicle with a small fuel capacity - my typical fill-up is about 3 quarts. What I want to know is if I'm filling up at a pump that has one hose for all grades do I get the grade I select, or is a significant part of my fill-up whatever was left in the hose from the last customer? Ultimately, this is a question about where the mixing happens, and how much gasoline is between the point of mixing and the end of the hose. Are gasoline pumps like those soda dispensers at bars that mix in the handle/nozzle? If not, how much gas containing hose is between the handle and mixer (inner diameter and length are fine - I can take it from there)?
For example, if the hose inner diameter is 1 centimeter then the area of the hose's opening is about .12 square inches, and if the distance from handle to mixer is 4 meters (about 13 feet), the hose volume is about 0.314 Liters, or about 1/3 of a quart. In this case, that wouldn't be a huge impact on a fill-up of 3 quarts. If the inner diameter is 2 centimeters, though, then the hose volume is about 1.3 quarts, a big, though not overwhelming, impact.