Question about gas :scratchhead:

[nilez]

I've always wondered how many gallons worth of gas the hose at the pump retains from the previous driver who filled up before I do.

Ex: Broke college kid fills his 1991 Honda civic hatchback with rust accents with 87 octane fuel. He grinds his gears pulling away from the pump, then I scream in to the same pump right behind him on the bike and select 91 octane. How many 91 octane gallons vice the previous 87 octane still in the hose am I truly putting in my tank if I top off with 3 gallons pumped total?

Any ideas?

[KawiSmurf]

I cant remember the last time I saw 91 octane at a gas pump, so since it's more likely to be 93 than 91, it's probably a moot point.

That being said, a gas pump hose holds about a third of a gallon. So that three gallons you top off with would average out to 92.3 octane if you get 93, or 90.6 if you happen to find a pump with 91.

Basically, nothing to stress over, it'll work just fine.

[nilez]

cool, thanks! And yes, I too have not seen 91 octane anytime recently, not sure why that's the number that came to mind.

[caddydaddy]

91 is all I could find in Maine, and down here in La, 91 is also the highest available.
I have heard that the hose, even though it seems thick has a vapor return line in it, so it doesn't hold as much fuel as it would seem.

[Rossco]

Yeah, high octane fuel and dental care are two things that they don't have in Maine.

[caddydaddy]

A few years ago, 93 octane was everywhere! Now 91 is the highest. Who knows why they stopped selling 93?

As for dental care, I liked my dentist in Portland!

[butcher bergs]

Blame the ethanol for the reduction in octane

[xrocket21]

A few years ago, 93 octane was everywhere! Now 91 is the highest. Who knows why they stopped selling 93?

As for dental care, I liked my dentist in Portland!

Maine decided to adopt califonia emissions is what I heard

In both maine and california, 91 is the highest you can get

[obsolete]

I know in places like Albuquerque and Denver the altitude is so high that the DA is obviously very high as well so the required octane for cars is lower therefore 91 only at the pumps. Doesn't help with this situation but interesting as well.

[Lucas]

A negligible amount.

Besides, I always drop the nozzle towards the ground so I don't dump gas all over my tank anyways.

[RandyO]

Blame the ethanol for the reduction in octane

uh, actually, no, ethanol has a higher "octane rating" than gasoline

unlike gasoline, ethanol is a single stable compount that ignites at a specific temp

[drop]

Maine decided to adopt califonia emissions is what I heard

In both maine and california, 91 is the highest you can get

massachusetts adopted california emissions years ago and we still have 93.

[xrocket21]

massachusetts adopted california emissions years ago and we still have 93.

[xrocket21]

http://forums.nasioc.com/forums/show...ghlight=octane

huh, that says it was simply due to lack of sales

Well all this 91 octane business got me thinking. So I called the State Attorney Generals Office on tuesday. They directed me to call the Dept. Of Agriculture, Quality Assurance, 207-287-2161. I also called the Maine Oil Dealers Association 207-729-5298, Chris Jackson. The Dept. of Agriculture told me this...."because of the lack of sales of 93 octane, at the discretion of the oil companies, by law, have the legal right to discontinue to stock 93 octane". And that is exactly what they have done. According to the Dept of Ag. the remaining 93 octane that they have tested (that is what they do, test the gas at every gas station for quality assurance) is at least 5 months old and probably equal to 91 or less octane. The gentleman said he hasn't heard of any station with 93 recently in the state. They are based outta Augusta. I was told it is up to the gas station to properly label the pumps, (which doesn't seem to be the case) and the auto manufacturers to provide cars that do not require 93 octane. The oil companies are in the free and clear. There is no law that states they have to sell 93 octane because certain vehicles sold require 93 a.k.a. the STi, WRX,all other turbo Subies, Audi S4 and A4, Saabs, Volvos, VW's. According to a source, 93 octane at Mobil on Center St. in Auburn has been 91 for several months now.
On a side note, in order for ExxonMobil to outright own any gas station they require that particular station to sell 2 MILLION gallons a year. On average gas stations in Maine only sell 270,000 gallons a year. The source of my info came from the Maine Oil Dealers Assoc. website. All Maine stations are privately owned, by like Dead River, who bought the rights to sell certain brand names. I know it sucks but there are alternatives, Torco Accelerator or VP MS109E. Have a good day.
Todd

[dhuze]

Yeah, high octane fuel and dental care are two things that they don't have in Maine.

You did know that the tooth brush was invented in Maine didn't you?















If it was invented anywhere else it would have been called a TEETH brush.

[Lucas]

ZING!

[ChicknStripEatr]

A gas pump hose is actually two hoses, one that runs inside the other. The diameter of the internal hose that actually dispenses fuel from the pump into your car is a little less than that of your pinky. The rest of that large black hose that the nozzle is connected to is used for vapor recovery to vacuum the volatile fuel vapors from your gas tank.

So at most, just a few cups of fuel actually remain within the hose.

[butcher bergs]

uh, actually, no, ethanol has a higher "octane rating" than gasoline

unlike gasoline, ethanol is a single stable compount that ignites at a specific temp

Even though I don't see how that's possible since my truck has developed this wonderful ping since the ethanol was introduced, I will take your word for it.

[Kurlon]

Even though I don't see how that's possible since my truck has developed this wonderful ping since the ethanol was introduced, I will take your word for it.

Ethanol is higher octane, nothing to argue there, it's a fact.

DRINK!

That doesn't mean the gas mix they're putting it in is as good as it used to be. In Maine for example a LOT of the additives that used to go into gas to stabilize it are no longer allowed, so what used to be viable if stored in a sealed metal container for a month or two is way down on octane in a week or two now. Plus ethanol sucks in water like there is no tomorrow, so the net result is you're getting overall crappier gas despite the higher octane rating of one component.

[butcher bergs]

So as the ethanol starts to attract moisture, the octane is not reduced?

[Lucas]

Yes, since the introduction of ethanol, gas "goes bad" earlier.

Causes lots of problems in boats as well

[obsolete]

So as the ethanol starts to attract moisture, the octane is not reduced?

Wouldn't adding water effectively increase the octane being that it is noncombustible? Kinda like water injection on FI engines.

[Kurlon]

So as the ethanol starts to attract moisture, the octane is not reduced?

The octane of the ethanol is not affected by the water around it.

[RandyO]

I think there is a misunderstanding of what octane or octane substitutes actually do

gasoline is a combination of many compounds each of which has different kindling temperatures

the purpose of octane is to stabilize the fuel so that it has a consistent kindling temp and the spark from the plug ignites the fuel rather than compression or hot spots in the combustion chamber

[butcher bergs]

I gotta do some reading on the topic. Doesn't the introduction of moisture reduce the efficiency of the burn thereby reducing the octane rating?