How gas pumps work...

[thejeepdude]

Well I've always wondered what happens when I go fill up my 2 gallon gas can with 91 octane after someone else has filled up their car with 87 octane with the same hose. Somewhere in a thread I saw it mentioned that the double wall hose was used to pump the 87 out of the hose before the 91 is dispensed. Well, today I was filling up at the local station which was just built a few months ago (all the latest equipment). A tech had one of the pumps completely apart and I asked him that question. He said that it is true, I am getting residual 87 octane before the 91 starts coming out. He said that there can be "up to a gallon" of the last used grade left in the hose! That means if I am filling a 2 gallon can, I am really only ending up with 89 octane. In fact, he said that there are really only 3 tanks in the ground... the 87, 91, and diesel. The 87 and 91 are mixed at the pump 50/50 to create the 89. He said the only way I can be sure that I am getting a full 2 gallon can of 91 octane for my ATV is to pump a couple gallons into a seperate can for the lawnmower or the vehicle I brought to the gas station before filling the ATV can up.



This kind of pisses me off. How many times have I paid an extra 30 cents for a gallon of gas and not gotten what I paid for? I want a refund!

 

[mazdarotary]

On a sorta unrelated note the other day I saw a woman driving down the highway with the filling nozzle and hose dragging behind the car. What a funny sight. I wish I had a camera at the time. It made my day. I was laughing all the way home.



I wonder how often this happens?



Chris

92 D250 CC LE

74 Mazda Rotary truck

83 Mazda RX-7 LE

00 Mazda Protege "hers"

 

[EMD Diesel Power]

Originally posted by mazdarotary

On a sorta unrelated note the other day I saw a woman driving down the highway with the filling nozzle and hose dragging behind the car. What a funny sight. I wish I had a camera at the time. It made my day. I was laughing all the way home.



I wonder how often this happens?



Chris







How about a locomotive going down the service tracks with the fuel stand still attached? :--) :--) Seen that happen a couple times... . people forgot to disconnect before moving the unit... . :-laf :-laf I know nickelonien has seen this happen too. and Im sure the other railroaders on TDR have thier own stories to tell.



Jeff

 

[nickleinonen]

How about a locomotive going down the service tracks with the fuel stand still attached? :--) :--) Seen that happen a couple times... . people forgot to disconnect before moving the unit... . :-laf :-laf I know nickelonien has seen this happen too. and Im sure the other railroaders on TDR have thier own stories to tell.

:-laf :-laf yeah i've seen a few funnies. we had one unit come through our service track that had a office depot shopping cart stuck to the front pilot [and we used it around the shop to move parts around] a couple of fuel stands ripped down, some derails ran over [there is an aluminum sign post we have on all our derails to mark them]



then there is the internal screw ups... like putting wrong traction motors, putting in wrong power assemblies in engines, pulling out wrong aftercoolers [on most locomotives, left side engine is right side carbody, right side engine is left side car body] pulling out wrong power assembly on GE engines. changing out wrong tracton motors, pulling out wrong cooling fans [on some units, the long hood is the front, but the short hood end is front electrically] and the mickey mouse work that gets done, like having the exhaust risers in the block crushed by water freezing around them and still running them [after having all 16 assemblies burned out with torch&arcair & all new assemblies applied] and having all the engine air box covers blown out by a little too much ether... :-laf

 

[JohnE]

I figured that out a long time ago. Why do you think the multi dispense pumps that have diesel use a separate hose?



I say find a smaller mom & pop station that still uses separate pumps.

 

[thejeepdude]

Originally posted by JohnE

I figured that out a long time ago. Why do you think the multi dispense pumps that have diesel use a separate hose?



I say find a smaller mom & pop station that still uses separate pumps.

I also figured that out a long time ago, but someone on here supposedly in-the-know said there's some sort of system that pumps the fuel out of the hose when you're done dispensing so that you get what you pay for. That may exist somewhere, but the circa 2003 pumps at my usual station aren't. Obviously, even if that system exists it would never work with gas/diesel through the same hose because of residue, but that wouldn't make a difference between grades of gas.

 

[Billy Diesel]

It is great for the gas station. The pumps probably cost less to produce 'cause less parts, and they have a chance to get paid more money for cheaper gas. What could be better (for them)?



That's why I like to ride my ATV and sled in groups. At the pumps, just make sure you aren't the first one to fill up!

 

[Sluggo]

Could work in your favor if the previous fill up was 91 and you want 87 !!

 

[CumminsPower98]

I never really thought of this. I will have to change my ways when fueling my XR600R, which I rebuilt with an 11:1 compression piston. It likes to ping in hot weather when pushed.

 

[lil red cummins]

i would think that as an alternative, buy 87 for whatever you have and then add 104 octane booster if the tank is less than say 5 gallons. that way you have better control over it. you should see the problem i have filling the model "A" ford up. i like to use a lead replacement additive. the old car just doesnt like pure unleaded. the valves tend to tick otherwise.

jim

 

[JohnE]

Back in the days of a Model A one could still purchase tetra-ethyl lead over the counter and mix at the pump. (I still don't understand why a 8:1 cr engine required higher octane. )

 

[lil red cummins]

my model A doesn't require high octane, in fact it runs fine on 85. it would probably run on 80 if there was such a thing. what it does need is the valve guide and seat lubricant that lead would provide. i can run normal low octane, but as i said, the valves tick for about 5 minutes when cold. they are just sticky because the oil runs out. i used to run Pyroil top lube, and just suck it in the vacuum line that runs to the windshield wiper. that would stop the ticking immediately. unfortunately you can't buy it anymore.



jim

 

[klenger]

Sun Oil Company (Sunoco) used to offer gas in about 8 grades by mixing regular and high octane. I don't know if they still do this or not since I haven't seen a Sunoco station in about 20 years.



I suspect there is more volume than just the gas pump hose. There has to some volume inside the pump, valves, fileters, etc. too. If you're driving a gasser, I suppose you could put the 1st couple of gallons in the vehicle fuel tank before filling the small gas can. Life's not perfect.

 

[thejeepdude]

Originally posted by klenger

Life's not perfect.

But the quest is never ending!