General Question

lrk's avatar

If a gas pump only has one handle, is there residue from different octanes in the pump / am I necessarily getting "my" octane?

Asked by lrk (757points) June 4th, 2010

At this sort of gas pump that only has one hose for all the gas types, does the gas I chose stay in the hose after I stop pumping?

If the next person chooses a higher octane gas, are they getting one hose-length’s worth of lower octane gas before they get their own?

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4 Answers

WestRiverrat's avatar

There may be a little (less than an ounce or two) residual gas left in the hose. It will not be enough to effect the next customer at all. The hoses are designed to empty when the nozzle clicks off, that is one reason why it takes a couple seconds between selecting your gas and the pump clicking on. It is priming the pump.

If the hose was kept full of gas, there would be no lag when you open the nozzle when you started pumping

lrk's avatar

@WestRiverrat Thanks so much! How does it empty? Does it get vacuumed or siphoned back out of the hose, somehow?

LuckyGuy's avatar

A tiny amount does stay in the hose, but it is insignificant. You might have a slug of 3 feet of old fuel but the diameter of the hose is only ¾ of an inch so that comes to 18 cubic inches of old fuel. Just about 1% of one gallon. Not worth worrying about. Relax.

MissA's avatar

Twas easily answered…but, a down-to-earth great question.

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