Single hose gas pumps
 

Some gas pump have one hose. If the person before me buys 87 octane when they are done is the hose still filled with this swill? When I start pumping 91 octane do I get a hose worth of 87 at the beginning? How much gas do you think stays in the hose?

To make this sound more important I should mention that sometimes I buy less than a gallon at a time for my motorcycle that requires 91 octane. Since first thinking of this I've been avoiding single hose pumps but I'm curious to know how they really work.

That's a good thought, one I've been wondering about too. At the Chevrons up here in BC, the only single gasoline hose is for their 94 octane stuff......

LOL@ swill!
I am fairly sure we are talking ounces. OK, I did a calculation for volume. I guessed at 1/2 inch inside diameter, and 6 feet long. 56.5 cubic INCHES. And according to Google.com, that is .24 gallons.

I bet you drive the car up right? How about pumping 1/2 gallon or so of this into your car, and then move to the can? This should clear the "swill"!:thumbup:

It's my experience that most pump hoses are connected to the top of the pump. When the car is full, and the pump shuts off, any of the gas that is in the hose drains down into the car. Take notice of this next time you are filling up.

Even if the amount of gas left in the hose = 0.25 gallon and if you are trying to fill your 1 gallon motorcycle tank with 89 octane, but the vehicle before you left 93 octane in the hose...

(0.25 x 93) + (0.75 x 89) = 90 octane

Since the amount left in the hose is probably less than 0.25 gallon, than the effects are even less.

(0.1 x 93) + (0.9 x 89) = 89.4 octane

An obviously, if the tank is larger than 1 gallon, the effext are even less still.

The math is simple, and I don't mean to point out the obvious, but sometimes it's just easier to see.

The hose is a lot longer than 6 feet more like 12-16 feet and don't forget the pump pipes too leading to the valve that switches the octanes.
Inside diameter is more like an inch in diameter unless there is a return hose for fumes. Sounds like you need to get to a three pump station.

I haven't seen 12-16 foot long hoses in RI in five years. All the hoses I see in RI and MA are 8'.

I figure you only get what's caught in the loop, about a cupful. This would make next to no difference on a 5 gallon fill in a car, but it is slightly worrying for something that only drinks small servings, though at a cupful per gallon, it would only dilute it to 90.75, and I doubt you'd tell the difference.

What kind of motorcycle? You might not even need anythign higher then 87.