Pump octane switch

[Digital2k2]

Say the pump you're going to use just pumped 87 octane and you select 93 octane... How much 87 are you going to get before the 93 starts flowing through the line?

It would be interesting to see the average pumps internals and how long the line that holds the previously pumped fuel actually is. I'm just imagining around half a gallon.

Looking forward to reading everyone's thoughts!

 

[Digital2k2]

So far this is the only thing I've found: http://online.wsj.com/article/SB122944043385810527.html

1/3rd of a gallon. But they just say the hose. Does that include down to where it changes over around the octane buttons?

 

[rshunter]

Originally Posted By: Digital2k2
So far this is the only thing I've found: http://online.wsj.com/article/SB122944043385810527.html

1/3rd of a gallon. But they just say the hose. Does that include down to where it changes over around the octane buttons?

The location of the buttons have no relation to where the valves are.

 

[Eddie]

When I worked at a gas station, I would drain each pump hose into a gallon can at the end of my shift. I ended up with ~ one gallon out of the 4 pumps or about 1 quart for each pump. A gallon of free gas was like gold to this poor boy.

 

[Digital2k2]

Originally Posted By: rshunter

The location of the buttons have no relation to where the valves are.


The reason I said around that point is because I found a picture of the internals of an older pump that made it appear it might switch around there. It would only seem fair that they bring them as close to where the hose attaches as possible though.

Originally Posted By: Eddie
When I worked at a gas station, I would drain each pump hose into a gallon can at the end of my shift. I ended up with ~ one gallon out of the 4 pumps or about 1 quart for each pump. A gallon of free gas was like gold to this poor boy.


Interesting. Hopefully it isn't much more than that up to the point where the octane switches.

 

[turf1]

the only sure way is to buy gas from those pumps that have 3 hoses, one for each grade. I have to do that when I buy gas for my ope engines, they call for 93 octane.

 

[Digital2k2]

Originally Posted By: turf1
the only sure way is to buy gas from those pumps that have 3 hoses, one for each grade. I have to do that when I buy gas for my ope engines, they call for 93 octane.


Went for a drive earlier by all the gas stations around here and sadly I only have 3, all are not top tier. At least there's a BP a few miles down the road with 3 hoses... they claim their additive would meet top tier standards. The other two are a 7-11 and WilcoHess.
I got a gallon of 93 with invigorate (haha) for the chainsaw.

 

[BearZDefect]

In a vehicle (where you're adding at least 10 gallons at a time) I don't think this residual gasoline of lower octane matters. If you're (understandably) concerned about it when filling your gallon jug for power equipment or toys then pump some gasoline into your vehicle first, then fill the jug with the pure premium.

 

[Digital2k2]

Right. How much is 1/3rd gallon or so of 87 going to lower the octane on a 15 gallon fill up of 93 anyway? Not enough to make a difference in most cases probably.
If I ever run the 93 octane tune on my truck I'll probably try to mostly get it at one of the 3 hose stations though. Especially if I bump the timing up too.

 

[BBDartCA]

Originally Posted By: Digital2k2
Right. How much is 1/3rd gallon or so of 87 going to lower the octane on a 15 gallon fill up of 93 anyway? Not enough to make a difference in most cases probably.


It would be 92.88235294 octane.

 

[lexus114]

Originally Posted By: BBDartCA
Originally Posted By: Digital2k2
Right. How much is 1/3rd gallon or so of 87 going to lower the octane on a 15 gallon fill up of 93 anyway? Not enough to make a difference in most cases probably.


It would be 92.88235294 octane.
Hahahaha!

 

[Digital2k2]

Oh well. Unless you only use the lowest available octane, these pumps most stations are switching to aren't that great.

 

[Audi Junkie]

We have all new pumps at our TT retailer, the blendy kind. I'm considering putting my card back in and shooting some 87 in to wash out the hose, but not worth it.

 

[Digital2k2]

Finally got a straight answer from ExxonMobil. Both Shell and BP didn't even address my question.

"The Weights and Measures Division of the National Institute of
Standards and Technology allows for a maximum volume of commingled product of 0.3 gallons. This requirement is met at all of our service stations
(0.3 gallons or less of commingled product)."