Lots of discussions about the one verses three gas pump hoses and how much of the low octane you get if you order 93 when using a single hose pump that pumps all grades.
The newer ("vapor recovery" and "drive away protected") setups will give you 87/91/93 whatever you order.
Here's how they work...
First customer of the day drives in, slides in his credit card, pulls the handle out, presses buttons, and the pumps load up. He squeezes the trigger, reducing system pressure, and they kick on and pump fuel.
When he finishes and replaces the hose handle, a sensor reads an increase in pressure, and the pumps back off. Most of the systems then wait until the transaction code is processed, and then depressurize the unit & hose clear down to the one way valve. Next time you gas up, look at the hose. See that metal ring about 2 - 3 feet from where the hose comes out of the housing? That's a combination valve/breakaway.
So, you drive up and order up some 93... there will be a few drops of low grade left in the hose, but that's it - a few drops, nothing more. Pull up to a newer station today & squeeze the nozzle handle before starting the transaction and note how much gas comes out - that's exactly how much "previous grade" you'd get, just a few drops will dribble out.
The newer ("vapor recovery" and "drive away protected") setups will give you 87/91/93 whatever you order.
Here's how they work...
First customer of the day drives in, slides in his credit card, pulls the handle out, presses buttons, and the pumps load up. He squeezes the trigger, reducing system pressure, and they kick on and pump fuel.
When he finishes and replaces the hose handle, a sensor reads an increase in pressure, and the pumps back off. Most of the systems then wait until the transaction code is processed, and then depressurize the unit & hose clear down to the one way valve. Next time you gas up, look at the hose. See that metal ring about 2 - 3 feet from where the hose comes out of the housing? That's a combination valve/breakaway.
So, you drive up and order up some 93... there will be a few drops of low grade left in the hose, but that's it - a few drops, nothing more. Pull up to a newer station today & squeeze the nozzle handle before starting the transaction and note how much gas comes out - that's exactly how much "previous grade" you'd get, just a few drops will dribble out.