Gasoline Expansion Puzzle

A Bigfoot is messin' with your mind by pouring in an extra bit of gas? (There is a story about college students doing this to their prof.)

Maybe it was this?

http://www.edn.com/electronics-blogs/anablog/4311370/Pranking-bosses-friends-and-competitors-

From the article:

"So exercise caution if you don't want to get caught in a prank backlash. It is much safer to do fun pranks like Analog Devices engineer Sandoe Thomsen did to a co-worker who was constantly bragging about the great mileage his VW Beetle was getting. Thomsen started adding gas to the tank. IDT analog IC designer Paul Brokaw worked with Thomsen at this unamed previous company at the time. Brokaw reminisces. "It was back in the 1950s when Beetles were rare. Sandoe began tracking this guy's mileage and adding gas to his tank. Remember the old Beetle had no gas gauge, making this occasional fill-up pretty hard to notice. I don't recall that they got it to 100mpg, but it was a big number. And then Thomsen cut him off, cold turkey. The guy went nuts and took the car in to get the mileage fixed. The VW mechanics confirmed to him that he was nuts."

That's it. I got some detail wrong, but the story is still the same.

I must admit though, I could easily see this prank being done in many places. This is just the instance that I remembered.

The gas tank can over flow (you proved it) the can maybe can't.

And all there is needed is a pressure low to make it overflow! We''ll maybe never know . . . Or was it the snow? Did it make the garage tilt so it spilt?

We did have a storm front come through Denver area and the barometric pressure changed with the warm front replacing the cold front on Sat/Sun. That would affect the gas tank regardless of the temp in the garage. Thanks.

Heat soaking.

Fueling engine in the cold, running the engine cold = stable temp. conditions.

The moment you stop operation and pack blower back in basement, remaining heat from engine must have transferred to fuel, did the overflow mess, and contracted again after, when things cooled down.

How much lower was the tank after the overflow?

used it to clear the drive of about 2 feet of snow, then I refilled the tank to the base of the filler neck
What do you think the temperature of the gas, still in the tank, was when you topped it up?

Could have been colder? Close to the engine warmer?

What a mystery!

My guess is that the heat from the blower engine caused a vapor bubble which forced some of the gasoline out of the tank.

But it was a day after it was used and it was cold engine when the gas was added.

What - no prize on offer for the correct answer? What a swiz! ;-)

Interesting how everyone is focusing on the density of the gasoline.

How about the change in shape of the gas tank with temperature?

The tank would have to contract only a small percentage to cause gas to work its way up the neck.

Doesn't quite add up.

Refueling was done outside, before running, colder/coldest.

i.e.: shrinkage would have been max. at this stage.

Next, basement warmer than outside, as explained by poster.

After reading several replies, I need to add a few details: The garage where the gas can was on the shelf and the snowblower was stored is a detached garage with no heat but well insulated and drywalled so it maintains a fairly constant temperature but rarely freezes, it is 30x24 with a loft above and 12' high ceiling in the lower level. No warm cars were parked in the garage either day. Both days had sun in the daytime but the garage does not change temp much since it is fully insulated and finished drywall with only 2 small windows at the peak ends above the loft, which has an open staircase from the lower level. I fueled the snowblower in the garage before using it on Sat night when the temp was 4 degrees F outside and refueled Mon AM when the temp outside was about 15 degrees F, but the snowblower was not used on Sun at all and should have been back to cold after sitting in the cold garage for more than a day unused and not started. I realize the engine would still have a little residual heat differential from being used on Sat PM but not enough to expand the fuel in the tank. I will offer a prize to the best explanation: You may come up the mountain and use the snowblower to clear my decks and the 1/2 mile of road to the street without charge! Since I filled to the neck of the tank on Mon AM I do not expect a lot of air left in the tank to cause tank expansion due to any increase in the ambient garage temp compared to when I noticed the gas overflow Mon afternoon.

OK, here goes.

Sometime during the day on Monday the sun shone through one or both of the small windows onto the gas tank of the blower, causing thermal expansion of the gas.

No basement in the garage to warm the concrete floor (it has a monolithic foundation poured on the bedrock base) to warm the gas in the can or tank, but a weather change Sun and Mon brought higher air pressure and a few degrees warmer temps. I am grateful for the input and I will allow more expansion room in the gas tank next time. Our barometric pressure hovers around 20-21 in Hg and water boils at about 88 degrees C., we have to adjust cooking times and use a pressure cooker to get a potato cooked!

Compare the relative thermal expansion of gas and iron (steel is similar).

..................linear .... and .......volume

From https://en.wikipedia.org/wiki/Thermal_expansion#Coefficient_of_thermal_expansion

open a gas station you'll make millions

My father owned a SOHIO gas station in Wooster, OH back in the 1940's and 1950's and I pumped a lot of gas out of underground tanks that were cold and we had to be careful not to overfill gas cans and mower gas tanks on hot summer days due to temp related expansion. Most gas caps are vented to allow for that but this time the gas was flowing out of the gas cap and running down over the snowblower to the floor. I think the best explanation so far is the trickster who adds and removes gas at night to trick someone into having better or worse gas mileage on a car but only the Abominable Snowman lives up here and he is still hibernating with the bears! But there has been no sign of forced entry and it would not record anyway since the snowblower has no odometer or hour meter to check gas consumption.

Well if the gas can was sitting on the concrete floor, the heat would be more likely to transfer from the can, than if the snowblower which was perhaps sitting on rubber tires....The snowblower tank is at air temperature, and the gas can is at floor temperature...

Sudden change of ambient vapor pressures. At elevated heights and with snow gong on, air becomes lighter. Gasoline just want to establish equilibrium at lower vapor pressures of surrounding air plus the elevation. It expands.

I know of Rev Dr John Piper who picked a Minneapolis, MN church after our years together at Wheaton College and he picked John Calvin as his model and has written a lot of books on Calvinistic theology and the path to Heaven.

So do you expect me to be him? Not even close.

No, he's human.

the answer to the mystery>http://alcoholrehab.com/drug-addiction/petrol-sniffing-gasoline-sniffing/

Do gasoline sniffers tend to spend a lot of time commenting on forums?

Tagline grammar is kinda 'strange'

That ain't all that's strange.

Perhaps the ethanol in the gas was absorbing moisture content.....?

https://www.youtube.com/watch?v=YeCyFxoWPpo

I'm not sure that that explanation holds up.

If there is a difference of pressure between the inside and outside of the tank: then that same difference of pressure will exist at the point where the gas is leaking out.

The fuel can is a 5 gallon PLASTIC one and the gas tank is a 1 gallon rectangular METAL one so the expansion would be diferent.

The material of the fuel can is irrelevant once the fuel is in the gas tank.

I meant to say the expansion or contraction of the containers due to temperature changes would be different for plastic and metal containers in the same location and the temperature of the metal tank would change faster than the plastic can. So any warming would expand the gas more rapidly when it was in the tank.

Lyn's theory is one possible explanation. I use lamps with magnifying lenses for work with small parts, and carry a warning about not leaving them where the sun's rays could be focused on combustible material.

Another possibility, possibly due to the sun's warming AND engine warming:

Gasoline VAPOR escaped via cap vent, or due to incomplete combustion, then re-condensed due to cold air.

You just saw the liquid residue.