[kuthair]

Ok, so here's a question. You pull up to the pump at a gas station, the guy before you just filled up his car with 87 octane. You put your credit card thru and select 93. How much of that 87 octane fuel is still in the hose before the 93 starts pumping thru?

[HyperM3]

None if you have independant hoses for each octane.

[kuthair]

^ good point... ok, but how bout for the pumps all share one hose, which is the case at a lot of gas stations.

[335xi]

Approximately one hoses worth.

No idea, but I doubt it is enough to worry about, if you are sticking at least a half a tank in I would think it is about 1% of what goes in your car, but I'm just pulling numbers out of my ass.

I guess you could just spray the first second of gas on the ground and then stick it in your car.

[HyperM3]

I dont think anyone here is a gas station fuel pump engineer, but Id have to guess not enough to affect the rest of the tankful.

[dmboone25]

Originally Posted by HyperM3

I dont think anyone here is a gas station fuel pump engineer, but Id have to guess not enough to affect the rest of the tankful.

+1--surely this amount would not matter...

[LarrySinNJ]

FWIW, I have on occasion filled up with Plus (89 Octane), with no noticable knocking or decreased performance.

[kuthair]

Originally Posted by dmboone25

+1--surely this amount would not matter...

as long as your filling up, I agree....but once in a while you have those times your driving home late at night and all u have is a fiver in your pocket.

[kuthair]

Originally Posted by Lrscpa

FWIW, I have on occasion filled up with Plus (89 Octane), with no noticable knocking or decreased performance.

I believe that...but I think a turbo'd engine is more susceptible to knocking.

[Jaws]

If this in the least bit concerns you, wait until you see a big $$ vehicle filling up. Chances are that they will be using premium, and just make sure you are next in line. But, it's not worth worrying about.

[HyperM3]

Or, find a gas station that has independant pumps.

[ages944]

The car has a knock sensor. Don't worry about it.

[CarbonE39m5]

Originally Posted by 335xi

Approximately one hoses worth.

No idea, but I doubt it is enough to worry about, if you are sticking at least a half a tank in I would think it is about 1% of what goes in your car, but I'm just pulling numbers out of my ass.

I guess you could just spray the first second of gas on the ground and then stick it in your car.

im gonna do that next time i fill up

[zoomy]

Originally Posted by kuthair

Ok, so here's a question. You pull up to the pump at a gas station, the guy before you just filled up his car with 87 octane. You put your credit card thru and select 93. How much of that 87 octane fuel is still in the hose before the 93 starts pumping thru?

Hi. First post…couldn’t resist…..flame me if you want!

Frankly, it depends on the dimensions (diameter and length) of the hose to a large extent.

You can do a quick calculation (gasp!) using conversion factors available on the internet. Let’s say that the diameter of the hose is 1 inch. The area is then pi (3.1415) r squared (or ½ diameter squared). So the area of a 1 inch diameter hose is (3.1415*.5*.5 = .785 inches squared). Multiply that by the length of the hose. Let’s assume that an average hose is 10 feet long. That’s 120 inches times .785 square inches. Multiply this and you get about 94 cubic inches. From the internet, you’ll find that 1 cubic inch = 0.0043 gallons, so .0043*94 = 0.4 gallons (just about).

Answer….you get about 4/10s of a gallon of 87 octane in the hose.

Assuming that you put $5 of 93 octane in your tank (at $3.50/gallon), you’d be putting in 1.4 gallons total, of which .4 gal would be 87 octane and 1 gallon would be 93 octane. If they mix evenly, your octane for that particular $5 fill would be about 91.3…..still above the minimum level recommended for a 335i. If you pay more per gallon, you'd have even less octane for your $5.

But, even though I agree that this is not anything to worry about, it IS a surprisingly large volume relative to a small “fiver” fillup, and definitely more than 1% for even a full tank.

Like I said….couldn’t resist…..

[STE92VE]

I wouldn't worry about the amount of 87 octane left in the hose as much as the overall quality of the gas that the station supplies to it's customers.

[DrGP]

Originally Posted by Lrscpa

FWIW, I have on occasion filled up with Plus (89 Octane), with no noticable knocking or decreased performance.

The key word would be noticeable. In reality there is a reduction in performance. Your car's sensors will adjust the timing to allow you to run on lower octane with no damage to the engine. You actually will get better mileage. Car and Driver did a test on this a few years ago and found that the more performance oriented you engine is, the greater the loss in performance with using regular VS premium, BUT in all cases, the drop in performance was not that great. That is probably why you don't notice it. BTW, one problem with running regular gas is that MANY brands of gas do not put the same amount of detergents in the regular gas as in the premium. But some do.

[GregL]

Originally Posted by zoomy

Hi. First post…couldn’t resist…..flame me if you want!

Frankly, it depends on the dimensions (diameter and length) of the hose to a large extent.

You can do a quick calculation (gasp!) using conversion factors available on the internet. Let’s say that the diameter of the hose is 1 inch. The area is then pi (3.1415) r squared (or ½ diameter squared). So the area of a 1 inch diameter hose is (3.1415*.5*.5 = .785 inches squared). Multiply that by the length of the hose. Let’s assume that an average hose is 10 feet long. That’s 120 inches times .785 square inches. Multiply this and you get about 94 cubic inches. From the internet, you’ll find that 1 cubic inch = 0.0043 gallons, so .0043*94 = 0.4 gallons (just about).

Answer….you get about 4/10s of a gallon of 87 octane in the hose.

Assuming that you put $5 of 93 octane in your tank (at $3.50/gallon), you’d be putting in 1.4 gallons total, of which .4 gal would be 87 octane and 1 gallon would be 93 octane. If they mix evenly, your octane for that particular $5 fill would be about 91.3…..still above the minimum level recommended for a 335i. If you pay more per gallon, you'd have even less octane for your $5.

But, even though I agree that this is not anything to worry about, it IS a surprisingly large volume relative to a small “fiver” fillup, and definitely more than 1% for even a full tank.

Like I said….couldn’t resist…..

Um...wow...

[teknochild]

Originally Posted by 335xi

Approximately one hoses worth.

no probably more about 2 hoses worth, the hose goes to the top, you dont think the tanks are in the roof do you?

im pretty sure the selector is about 1/4 of the way up the unit.. so.. a lot

i would be willing to bet at least a gallon



makes me want to use the three hose type pumps





on an off note, i had a dream (or nightmare rather) the other day that i filled up with diesel!!! oh the horror, i was running around the station wigging out trying to figure out what to do, i ended up sucking it out of the tank with a piece of bamboo??!!!

let freud have fun with that

[teknochild]

zoomy, those hoses have an interior diameter of more than 1 inch, i would say AT LEAST two inches, which would do much more than double your calculations

[McDeb]

Originally Posted by zoomy

Hi. First post…couldn’t resist…..flame me if you want!

Frankly, it depends on the dimensions (diameter and length) of the hose to a large extent.

You can do a quick calculation (gasp!) using conversion factors available on the internet. Let’s say that the diameter of the hose is 1 inch. The area is then pi (3.1415) r squared (or ½ diameter squared). So the area of a 1 inch diameter hose is (3.1415*.5*.5 = .785 inches squared). Multiply that by the length of the hose. Let’s assume that an average hose is 10 feet long. That’s 120 inches times .785 square inches. Multiply this and you get about 94 cubic inches. From the internet, you’ll find that 1 cubic inch = 0.0043 gallons, so .0043*94 = 0.4 gallons (just about).

Answer….you get about 4/10s of a gallon of 87 octane in the hose.

Assuming that you put $5 of 93 octane in your tank (at $3.50/gallon), you’d be putting in 1.4 gallons total, of which .4 gal would be 87 octane and 1 gallon would be 93 octane. If they mix evenly, your octane for that particular $5 fill would be about 91.3…..still above the minimum level recommended for a 335i. If you pay more per gallon, you'd have even less octane for your $5.

But, even though I agree that this is not anything to worry about, it IS a surprisingly large volume relative to a small “fiver” fillup, and definitely more than 1% for even a full tank.

Like I said….couldn’t resist…..

Well, that's pretty darn impressive.

But I got a headache just reading it. Nice post.

[zoomy]

Originally Posted by teknochild

zoomy, those hoses have an interior diameter of more than 1 inch, i would say AT LEAST two inches, which would do much more than double your calculations

teknochild, Since I guessed at the diameter (don't have a gas pump in the house!) I would defer to your assessment.

to gregL and McDeb...I got a headache writing it. Whooo!

Just wanted to have a little "fun" with the response - did think it was an interesting question though, and I'm surprised with the answer, even if on the low side.

[teknochild]

yea i dont even care that some asshole is getting a gallon ro two of MY 93 octane, he can have it, i just dont like that im getting his shitty ass 87 octane

im going to start hanging out at gas stations and waiting for other HP cars to fill up and pulling in behind them lol