I was in the car today listening to the radio talk show, where the host discussed the raising crude oil and gasoline cost (blah blah blah...), and she talked about an interesting point I have never thought of.

Years ago (~15 years), the older gas pumps (the ones where you lift the lever to had separate pumps and hoses for each gas line. So basically, the premium grade fuel pumps had it's own pump and hose.

The newer pumps are digitally operated that we are all familar with. You push a button with desired octane and start filling.

Anyways the lady was saying, you can get "the better higher octane" gas for the price of regular if you filled up after someone who filled up their vehicle with premium, and you selecting the regular grade. (I bet theres a huge misconception among the public between octane rating and quality of gas).

Does anyone know how much fuel is left in the pump and hoses if the previous/next user at the same pump selects a different octane?

Personally, I don't think my TSX performs differently on 91octane of 90.5 octane, but I guess theres performance differences on must-have-high-octane cars like modded turbos or 335i's.

 

at the station i use, you can pull the trigger up and no gas will flow out for a second and then it will flow out as if the pipe/hose was empty.

 

depending on what gas station i go to i got some around where i gotta "throw up the lever" to start the pump and to "throw it down" to cut off the pump. you can maybe get like 1/100 of a gallon for free(and i usually do that) to empty out whats in the nozzle. but i run regular.