How does a gas pump know to shut itself off? (1981)

Customer came in soaked in gasoline.

Into an electronic store...

She got very fast service as we rushed to get her out the door.

Apparently there was an “incident” at the pump.

We suspected lack of brains

[1] https://www.pownetwork.org/bios/h/h135.htm

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Your vehicle is designed to operate on unleaded gasoline with a pump octane number of 87 or higher. Use of a lower octane gasoline can cause a persistent, heavy metallic rapping noise that can lead to engine damage.

We recommend using gasoline containing detergent additives that help prevent fuel system and engine deposits.

In addition, in order to maintain good performance, fuel economy, and emissions control, we strongly recommend, in areas where it is available, the use of gasoline that does NOT contain manganese-based fuel additives such as MMT.

Use of gasoline with these additives may adversely affect performance, and cause the malfunction indicator lamp on your instrument panel to come on. If this happens, contact your authorized dealer for service.

Some gasoline today is blended with oxygenates such as ethanol or MTBE. Your vehicle is designed to operate on oxygenated gasoline containing up to 10 percent ethanol by volume and up to 15 percent MTBE by volume. Do not use gasoline containing methanol.

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Dealing with the octane number is easy. Just don't use gas with a lower octane than your manual calls for. You can use a higher octane if you want, but it won't really do anything other than cost more. You'll get the same performance, wear, pollution, and mileage as you would with the octane number given in your manual.

Here's a random example I found: https://i.imgur.com/nDkwl0i.jpg

It doesn't actually say "octane", but note that it says "MIN.(R+M)/2", and (R+M)/2 is what you'll see on the pump too, as in this example image: https://img.hmn.com/fit-in/900x506/filters:upscale()/stories...

(This is for the US. I would assume other countries are similar.)

As others have said, your manual will tell you, but a good rule of thumb is if you don't have a high performance vehicle or an engine with a turbo or supercharger, 87 should be fine.

So use high-octane in turbocharged cars and low octane for non-turbocharged cars. (If you use too high an octane in your car, it won't hurt anything but your wallet.)

If you're racing a turbo car you might need close to 100 octane, which cannot easily be bought but it can be made by adding toluene to your gas tank (google it).

Other than that check your owner's manual.

Most stations just go with the refinery default additive mix, which is typically pretty good. Some national brands go with a slightly better additive mix. Some national brands go with a cheaper additive package. You need to be a large chain to afford to pay a chemist to design an additive mix though, so the majority of stations don't.

You know, for the types that tend to drive off with the dispenser nozzle still in the tank.

1) Signs that you should not use a cell phone at a gas pump are largely a result of a string of incidents in the '90s in which gas station fires occurred when the operator was using a cell phone. Causation was assumed and the warning decals were put on pumps. Later research by the Petroleum Energy Institute, an industry group, did not find any incidents that were actually caused by cell phones. The correlation may be due to a confounding factor, that people talking on cell phones are more likely to get in/out of their vehicle while pumping which could cause a static discharge. The PEI reports that, in general, improvements in vapor management in vehicles and fuel dispensers makes the risk of static discharge causing a fire low at modern gas stations.

2) General industrial best practice, and various safety regulations which are influential but not necessarily applicable to consumer gas stations, prohibit the use of electronic devices near flammable substances unless those devices are certified to be safe for that use. While many cell phones are probably "intrinsically safe" (do not involve potentials high enough to reasonably produce a spark), few are actually verified to that standard by the manufacturer (would need to be labelled "intrinsically safe" by the manufacturer following their safety analysis). In a safety-regulated environment they would thus be prohibited out of an excess of caution.

On the balance it seems likely that cell phone use at the fuel dispenser is probably not a hazard, but it never hurts to minimize distractions and extra factors when handling something potentially explosive.

I've never noticed a measurable difference when filling up the 20 gallon tank in the truck.

I suspect you'd have to buy a LOT to make a meaningful difference.

It was an accident. Repair costs for customers were handled through the gas station's insurance.

Yes this is a thing and happens semi-often.

Keep in mind I was servicing over 75 locations and each had at least 3 tanks.

The most common way for water to get into the tanks was through the fill ports that the fuel delivery drivers filled the tanks with.

Seals could go bad, or the driver could forget to close a lid 100% of the way. Couple that with high water from rains and you’d typically get a high water alarm.

I think our system was setup to alarm if there were more than 3 or 4 gallons in a tank. These tanks are enormous. I don’t remember the capacity but they had many thousands of gallons of fuel.

Water goes to the bottom of the tank naturally and sets off an alarm. This alarm also stops the pump from running.

We’d call out a vacuum truck to pump the bottom of the tank (usually this cost A LOT of money. $1000 for 15 minutes of work)

Then we’d fix the entry point where water came in. If the alarm cleared on the system, we could turn the pump back on.

Only reason I know this is because premium gas in California used to be 92 octane. So the three choices were 87, 89, and 92. When we dropped to 91 octane, a lot of the stations near me had to swap out the yellow sticker on their mid-grades to read "88.5". That was my clue that the ratio had not been adjusted yet.

I agree that the environmental impact is a big problem. But perhaps if more people traveled, we would be more likely to get the kind of international cooperation we need to tackle climate change systemically.

For the first decade of my driving life that’s how I did it as well. But that now seems to be such a distant memory as I am 100% of the time just paying with a credit card at the pump.

Paying before pumping became a thing when gas went to $4 a gallon several years ago. Stations had a lot of people driving away without paying and the amount stolen was below what the police would investigate.

You can often pay at the pump, and they way they work is they authorize a certain amount ($75, I think) against your card, and then when the station settles at the end of the day, the actual amount will be applied. I have exceeded American Express's hold limit a couple of times during cross-country drives, and had to talk to their fraud department..

Pumps with one hose are cheaper. You'll probably get a dribble of whatever grade the previous customer chose from what was left in the hose. But diesel will always have it's own hose.

The funny thing about precisely stopping the pump - prices in the US seem to always have 9 tenths of a cent added to them - like $2.599 per gallon. If you purchase exactly one gallon, and hand over $2.60, there's no way to get that tenth of a cent change. I expect it was originally a marketing thing, and now it's a custom.

https://upload.wikimedia.org/wikipedia/commons/6/68/Chicago-...

via: https://en.wikipedia.org/wiki/Ferris_Wheel

It's strange, but I come across these idioms from other cultures back-to-back as I read stories on HN. That's most likely due to the blood, sweat, and tears people put into communicatng on here. Or, maybe language is a bone of contention, and the idioms are simply a breath of fresh air that grabs us by the nape. Whatever the cause, the languages differences sometimes chill me to the bone, maybe they even cause a gut feeling as they hit a raw nerve.

I suppose it's better to be up your ears in idioms, rather than waiting with bated breath.

Thanks for letting me go off on a tangent!

Viceversa to "grab by the throat" translates literally to "prendere per la gola" that actually means to "Tempt through food".

It's super annoying, unless it's raining or really cold out.

I don't care what the idea is, it's annoying, insulting, and backwards.

For UK pumps you actually need to stand there and physically hold the pump nozzle the whole time. If you let go it is spring loaded and it stops pumping.

Of course, you don't have to look right at it while it is pumping...

I do watch my car while i am doing some other stuff or looking at my phone, but seen some other automation related stuff that makes me lazy. Like not locking the door at home when going out, because it's automatic.

This all seems to be pretty normal where I'm from.

I’ve done this hundreds if not thousands of times and it only didn’t work once, for the first time, a few months ago when I was filling my UHaul in Queens to move out of New York City. It was fitting.

Maybe they should remove those flip-up latches if they want to prevent people from doing that.

You don’t need to walk away, I generally just zone out watching the volume and price display scroll.

Are we really pre-mixing air+gasoline into the tank? Isn’t that a much higher risk of sudden explosion, compared to a tank with only carburant and no comburant?

The linked article invoked the Bernoulli effect to compare the pressure of the pumped gasoline in the pipe to the pressure of the ambient air; the Bernoulli effect is based on conservation of energy and does not apply here because the pumped fuel is not magically transforming into ambient air in an energy conserved way.

In normal conditions fluid has lower pressure if: (a) it was flowing and is now moving faster because of a geometric constriction (b) it is being sucked (i.e. being pulled into a lower pressure region than ambient)

Moving fluid has higher pressure if: (c) it was flowing but isn't flowing as fast due to a geometric expansion (d) it was pushed (i.e. coming from a higher pressure area than ambient)

Note that in the case of a fan in a tube, the fluid has lower pressure than ambient behind the fan, and higher pressure than ambient after the fan.

The hammer idea is new to me. I spent several years working on cars and still like to wrench on the side.

Um, no.

It seemed to me that sometimes the angles would mean the gas splashed off the filler tube in the wrong way and confused the dispenser. There's a bunch of different ways to run a filler tube, and different dispenser handles, so I adapt.

In my case, my first vehicle was older than me, so you don't exactly complain to the manufacturer that it has trouble filling at some stations. When newer vehicles acted the same way, I already knew how to jiggle the handle to fill up, so I just wouldn't get to wash my windows at the same time as I filled up, if I went to the wrong station. I wasn't ever one to buy stuff inside while the vehicle was filling, so not a big loss of functionality.

I would feel fairly comfortable using the auto-shutoff. I have had it fail twice in my life. But, because the tip of the nozzle is so near the exterior of the tank, and the tank is becoming a bottleneck there, there is sometimes a little splashing that gets on the paint.

vented fuel tanks began in the 60s. Many older cars have absolutely no vent valve to speak of -- the vapor is dumped from the fuel cap, which acts as a vent; meaning the vent isn't present during fill-up on this style of design.