As the storage tanks at petrol stations are buried underground, the daily temperature cycle doesn't significantly affect the temperature of the contents in the tank - there's a lot of heat capacity in the earth surrounding a buried tank.
Vague calculation suggests that wine cellars at a depth of more than about 11 feet feel no effect from the *annual* temperature cycle!
Yes, the energy in fuel is proportional to the mass.
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>>Yes, the energy in fuel is proportional to the mass.
Indeed, NC.
Problem is that it's a lot harder to measure mass flow rate than volume flow rate: so it would be prohibitively expensive (though technically possible) to measure & meter the mass flow rate of petrol from a petrol pump into a car's fuel tank.
I think that the figures that the OP lists would have been arrived at by volume x density = mass calculations. In practice, a sea-going oil-tanker would be parked-up by a land-tank in Rotterdam (or somewhere). The density of the petrol would be measured, then a volume of petrol pumped onto the oil-tanker. Thus the mass of petrol loaded is calculated; of both commercial and vessel-stability interest.
Interesting thought: there may not be much variation in petrol density arrising from temperature changes; but, what about inherent variations in the density of the petrol itself? From vague memory, petrol can vary in density from about 0.69 g/l to 0.72 g/l @ 15 Deg.C(happy to be corrected on this). That's about 4%. Maybe that could explain why some people report getting higher mpg rates from one brand of petrol compared to another, perhaps the premium fuels are higher density than supermarket fuels?
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For what it's worth, this was posted recently on a US board:
"GAS PUMP TIPS
I don't know what you guys are paying for gasoline.... but here in California we are also paying higher, up to $3.50 per gallon. But my line of work is in petroleum for about 31 years now, so here are some tricks to get more of your money's worth for every gallon..
Here at the Kinder Morgan Pipeline where I work in San Jose, CA we deliver about 4 million gallons in a 24-hour period thru the pipeline. One day is diesel the next day is jet fuel, and gasoline, regular and premium grades. We have 34-storage tanks here with a total capacity of 16,800,000 gallons.
Only buy or fill up your car or truck in the early morning when the ground temperature is still cold. Remember that all service stations have their storage tanks buried below ground. The colder the ground the more dense the gasoline, when it gets warmer gasoline expands, so buying in the afternoon or in the evening...your gallon is not exactly a gallon. In the petroleum business, the specific gravity and the temperature of the gasoline, diesel and jet fuel, ethanol and other petroleum products plays an important role.
A 1-degree rise in temperature is a big deal for this business. But the service stations do not have temperature compensation at the pumps.
When you're filling up do not squeeze the trigger of the nozzle to a fast mode.
If you look you will see that the trigger has three (3) stages: low, middle, and high. In slow mode you should be pumping on low speed, thereby minimizing the vapors that are created while you are pumping. All hoses at the pump have a vapor return. If you are pumping on the fast rate, some other liquid that goes to your tank becomes vapor. Those
vapors are being sucked up and back into the underground storage tank so you're getting less worth for your money.
One of the most important tips is to fill up when your gas tank is HALF FULL or HALF EMPTY. The reason for this is, the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks
have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.
Another reminder, if there is a gasoline truck pumping into the storage tanks when you stop to buy gas, DO NOT fill up--most likely the gasoline is being stirred up as the gas is being delivered, and you might pick up some of the dirt that normally settles on the bottom. Hope this will help you get the most value for your money."
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Water pipes are usually about 2 foot 6 inches (750mm) below ground , deep enough to be protected from hard frosts and hot spells, and the water that comes out of the cold tap is typically 55f what ever the weather
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But the temperature might vary more significantly depending on whether they had just had a delivery. How is petrol stored at depots - below ground, or in those big tank things you see above ground? So petrol delivered on a hot day to a garage whose stocks had been low might be well above ground temperature?
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Does all this info apply to diesel as well?
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Temperature of petrol is a hot potato.
There are lots of complaints from garage owners who had petrol deliveries which shrank. In summer, the petrol would be warm in the refinery tanks, warm in the long above ground pipes to the tanker loading stands, and warm in the tanker. The tanker would deliver the warm fuel and it would quickly cool underground, and shrink. The station would telephone the sales dept. with merry hell to play. This problem reached a peak at the time when deliveries first changed over to printed delivery notes which were signed without verifying the amount in the road tanker, after climbing on top and dipping the compartments was banned by H&S law in the 1990s.
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About the only way for a consumer to be caught out by the contraction of hot fuel - especially diesel still hot from the refinery - is to but the fuel soon after a delivery of said hot fuel.
In most other circumstances, the daily temperature range experienced by the fuel in the storage tanks is less than, or comparable to a typical pump delivery error.
In general, advice to buy fuel at a particular time of day deserves to considered along with other urban myths.
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These matters were covered in a long report by the National Weights and Measures Laboratory in Middlesex in 1999. From this report, I'd conclude that the most a motorist in Britain would be likely to lose (or gain!) from temperature variations is about 2%.
Here's a few extracts relevant to this thread:
"...Hot fuel [eg petrol]Temperature > 24°C Approx. 1% volume difference from 15°C
Warm fuel Temperature > 17°C Approx. 0.25% volume difference from 15°C
Cool fuel Temperature < 13°C Approx. 0.25% volume difference from 15°C
Cold fuel Temperature < 6°C Approx. 1% volume difference from 15°C..."
"...Typically, in the region of ambient temperatures, petrols will expand or contract by 0.12% volume for each ºC change in temperature while diesel fuels will change somewhat less, 0.08% volume/ºC. Thus relatively small changes in temperature will result in significant changes in volume; 2ºC will result in 0.25% volume change for a typical petrol and 8ºC will result in a 1% change, while the same temperature changes will affect diesel volumes by 0.16% and 0.6% respectively..."
"...Fuel left to stand in these pipes will, with time, come to the ground temperature. The volume of these pipes is such that on sites with a high proportion of small volume sales and with significant intervals between sales the effect will be that fuel is sold at a temperature close to the seasonal average temperature. On busy sites with a high proportion of complete vehicle-tank sales, fuel will be drawn from the storage tanks and dispensed direct to the motorist and, although some heat transfer will take place between the flowing fuel and the ground, fuel will be dispensed at a temperature closer to that of the storage tank..."
"...At this point no mention was made of the reverse situation where cool or cold fuel may allow the retailer to sell a greater volume than they receive when fuel expands in retail storage. However, the PRA survey of retailer stock losses shows that this situation arises
regularly with diesel fuel (Fig 2)...."
Here's a link to their full report (65 pages long and for enthusiasts only):
tinyurl.com/3ojqzm
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