Gas pump question

[Tom M]

At lunch the other day a former coworker (Harley rider) was saying that when you select high octane gas at the pump you get quite a bit of low octane fuel because the valve that switches between the different grades is underground, and the gas pump hoses are connected 8 or so feet high. He contends that you get a gallon or so of whatever grade was selected before you got to the pump, which is most likely the lowest least expensive grade these days. That's significant if you only pump 3 or 4 gallons. I always assumed the switch between grades took place inside the pump itself, so I would only be getting a small amount of whatever grade was in the pump hose before I got there.

 

So...does anyone here know for sure how much 87 octane gas I might be getting when I select 92 or 93 at the pump?

[BRENTTODD]

If you are filling up where there are a diffrent nozzel for each grade there is no comingling thats how mine are set up. If there is only one nozzle for all grades u might get a little of the last grade but its not very much at all. A big varible would be where the pump is located in the ground or in the pump itself. The fuel compaines are very greedy bunch and there are a lot more company owned gas stations then mom and pops like my familys. They dont loose money or product. There have a very good check valve system to let the fuel drain back to the line but not to the tank to keep its prime. Thats why the pump runs for a second before it acuallys pumps. There is not much $$$ to be made on our side of the fuel world if we let a half gallon of super go for the regular price to would be big $$$ at the end of the day. To wrap it up you could get a little resdule fuel in the line but it wouldnt be enough to measure or make a difference.

Now if there is vapor recovery systems in your state then if not maintaned they fill up with fuel from people toping there tanks off just streach the hose out and pull the boot on the nozzle back and it comes flying out I have seen about a half gallon from doing that. Just remeber u get nothing for free any more

[Dan M]

At lunch the other day a former coworker (Harley rider) was saying that when you select high octane gas at the pump you get quite a bit of low octane fuel because the valve that switches between the different grades is underground, and the gas pump hoses are connected 8 or so feet high. He contends that you get a gallon or so of whatever grade was selected before you got to the pump, which is most likely the lowest least expensive grade these days. That's significant if you only pump 3 or 4 gallons. I always assumed the switch between grades took place inside the pump itself, so I would only be getting a small amount of whatever grade was in the pump hose before I got there.

 

So...does anyone here know for sure how much 87 octane gas I might be getting when I select 92 or 93 at the pump?

 

There was quite a bit of discussion about this issue on the BMW sporttouring forum some time back. I seem to remember that someone with actual knowledge of such things said the valve was at the pump and not underground and the hoses did not hold much fuel. It would follow that the plumbing from the valve to the nozzle couldn't hold more than a pint or two so if you are buying several gallons there won't be much dilution.

Of course this is all hearsay but seems to make good sense.

[BRENTTODD]

There was quite a bit of discussion about this issue on the BMW sporttouring forum some time back. I seem to remember that someone with actual knowledge of such things said the valve was at the pump and not underground and the hoses did not hold much fuel. It would follow that the plumbing from the valve to the nozzle couldn't hold more than a pint or two so if you are buying several gallons there won't be much dilution.

Of course this is all hearsay but seems to make good sense.

 

There right it is all about what pump you have. In my case and i would think its the same for everyone when your contract is up for your brand .You negoaite what you are looking for and if you need new pumps thats what you go after the catch is they pick the pumps. Therefore the valves are set up for the type of pump you are working with our pumps have two sets of valves one on the pump side one on the tank side. I dont know why two but i do now it has to do with holding the prime of the line so the pump dosent have to pull so hard. My pumps are odd though the guys who repair ours say that we are

the only station in Nj with the pumps we have.

[Tom M]

Thanks guys. I assumed it wasn't really an issue but didn't want to argue with the guy since I had zero facts to back up my assumption .

[Garsdad]

Let's see.... 4 islands with 4 pumps each and three grades of fuel each would mean 48 valves underground, and 48 separate lines coming up. Or, you put the valves in the pumps and plumb three lines to each island...

 

In most cases where government is not involved, logic rules.

[BRENTTODD]

We have 2 islands 3 grades of product. One line from each tank T ed off for both islands. One valve at tank side one at pump side for each product. One pump for each grade. One pump motor works dispencers on each side of the pump. Thats how the the layout is here. There is so many ways there done and a lot depends on state fedral or who you pay of in the position of power in your nieghborhood. So for me thats three lines nine valves.

[belfastguzzi]

It would have to be grossly illegal if the pump advertised a grade, at a price, but actually delivered a different grade!????

[v11cafe]

It would have to be grossly illegal if the pump advertised a grade, at a price, but actually delivered a different grade!????

How about if the pump says 15lt and you get 14.80lt???

There was some time ago an investigation done about fuel quantity and quality in Greece,

and as I see it...you pay like a fool... and you get less...grade/liters.

Good thing that a Guzzi is not so sensitive,...as other bikes

[docc]

The best information I had ever seen on this was that the 'transition' could contain about 3/4 gallon, or 3 liters, of the last fuel pumped.

 

That would lower your 91 octane fuel to 90.25 on a 4 gallon fill up.

 

Worse yet, what is 10% ethanol doing to the octane rating and the relative air/fuel ratio? My Sport seems most unhappy with the fuel lately . . .