Sylvie Willis
There is a common belief that filling up your car at night or early in the morning, when the temperature is cooler, will get you more fuel for your money. This is because fuel expands when heated, so when the fuel is cooler and denser, you get more of it. However, this may not be the case, as most fuel stations store their fuel underground, where the temperature is constant throughout the day. Additionally, many gas pumps are temperature-compensated, displaying the volume the fuel would have at 15°C (59°F) rather than the actual volume. While you may save a little money by filling up when the fuel is cooler, it is unlikely to be significant enough to warrant changing your schedule or routine.
| Characteristics | Values |
|---|---|
| Best time to fuel your car | Early morning or night when the temperature is cooler |
| Reason | Fuel expands when heated, so cooler fuel is denser and you get more amount of fuel for the same price |
| Flaw in the theory | Most fuel stations have their tanks underground, where the temperature is constant throughout the day |
| Gas pumps in Europe | More and more gas pumps are temperature compensated, i.e., they display the volume the fuel would have at 15°C (59°F) |
| Temperature difference | A 15-degree difference results in a 1% gain in volume, which is only a few cents' difference in the first gallons pumped |
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What You'll Learn
Fuel your car when it's cool to get more fuel for your money
Fueling your car in the morning or at night when it's cool has been a long-debated topic. The theory is that since fuel is denser when it's cold, you would get more fuel for the same amount of money. While this makes sense in theory, there are a few flaws to this idea.
Firstly, most fuel stations store their petrol or diesel underground in large, well-insulated tanks. This means that the temperature of the fuel remains relatively constant, and you would typically get the same temperature fuel regardless of the time of day. Additionally, the changes in density due to temperature are minuscule and would only make a marginal difference in the amount of fuel you receive.
Furthermore, waking up earlier or going out of your way to fuel your car at a specific time may not be worth the potential savings. The extra fuel burned during the trip to the station at a colder time of day may cancel out any savings from the denser fuel.
Instead of focusing on the temperature of the fuel, there are other effective strategies to get more fuel for your money. One strategy is to observe fuel prices, as some stations offer cheaper petrol at different times of the day. Another strategy is to drive more economically by maintaining proper tire inflation, changing your oil regularly, and avoiding overstressing the engine with hard accelerations.
Additionally, you can improve fuel efficiency by reducing the weight of your vehicle, removing roof racks when not in use, and planning your route to avoid stop-and-go traffic. These methods are more reliable ways to save money on fuel than focusing on the temperature of the fuel.
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Fuel density is higher in the morning
However, the actual amount of money saved by filling up in the morning is negligible. A 15-degree difference in temperature would only result in a 1% gain in volume, translating to only a few cents' difference. Additionally, most fuel stations store their fuel underground in large tanks beneath a thick layer of concrete, which acts as an insulator and keeps the fuel at a constant temperature. Therefore, the temperature of the fuel you are pumping into your car is likely to be the same regardless of the time of day.
Furthermore, in some places, such as Europe, gas pumps are temperature-compensated, meaning they display the volume the fuel would have at 15°C (59°F) rather than the actual volume. In these cases, there is no advantage to filling up your car at any particular time of day.
While it is true that fuel density is higher in the morning, other factors such as the constant temperature of underground fuel storage tanks and the use of temperature-compensated gas pumps mean that the advantage of filling up your car in the morning is minimal. The small difference in cost is unlikely to be worth changing your schedule or routine.
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Fuel temperature fluctuates in the pump dispenser
Fuel temperature can indeed fluctuate in the pump dispenser, and this can be influenced by a variety of factors, including the time of day, the season, and the design of the fuel station.
During the day, the sun can warm the fuel sitting in the pump dispenser, leading to a temperature difference between the first few gallons pumped and the subsequent ones. This temperature difference can be as much as 8°F to 17°F, as observed in some tests. However, the impact of this temperature difference on consumers is relatively minor, resulting in only a 1% gain in volume for a 15-degree difference, which translates to just a few cents' difference.
In colder regions, the temperature of the fuel in the lines and dispensers can drop significantly when sitting idle overnight. This can cause the fuel to become more viscous and affect the speed of the pumps, making them slower in the morning until they warm up. Additionally, cold temperatures can cause issues with the lubricant used in the pumps, making it thicker and potentially impacting pump performance.
The design of the fuel station can also play a role in fuel temperature fluctuations. If the underground pipe is too shallow or the dispenser is under direct sunlight, the fuel temperature can increase. Improving the piping system, such as by adding insulation or relocating the pipes, can help mitigate this issue.
Furthermore, the presence of foreign matter or dirt in the pump can also affect fuel temperature. Disassembling and cleaning the pump regularly can help maintain optimal performance and prevent temperature fluctuations caused by blockages or restricted flow.
To summarize, fuel temperature fluctuations in the pump dispenser can occur due to various factors, including daytime temperature changes, seasonal variations, fuel station design, and pump maintenance. While some of these factors may have a minor impact on fuel volume and cost, they are generally not significant enough to warrant changing one's schedule or routine. Regular maintenance and improvements to the fuel station design can help mitigate temperature fluctuations and maintain efficient fuel dispensing.
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Gasoline can sit for days in an underground tank
When it comes to maximising your fuel efficiency, there are a few factors to consider regarding the best time to fuel your car. One factor is the temperature of the fuel. Warmer fuel expands, and you may end up with slightly less fuel for your money. However, the difference in volume due to temperature changes is minimal and not enough to significantly impact your schedule or routine. For example, a 15-degree difference would only result in a 1% gain in volume, which equates to just a few cents' difference.
Another factor to consider is how long the gasoline has been sitting in the pump dispenser, which can be warmed by the sun. At underground tanks, it is common for gasoline to sit for hours or even days between fill-ups, whereas a typical filling station tank may be replenished daily or more frequently. As a result, the gasoline you pump into your car may be cooler if the underground tank has been recently filled, which could marginally benefit you as a consumer.
Now, let's focus on the statement, "Gasoline can sit for days in an underground tank." This is indeed true, and it's important to understand the implications and considerations surrounding underground fuel tanks.
Underground fuel tanks, or USTs (Underground Storage Tanks), are commonly used to store various liquids and regulated substances, including gasoline, diesel, and heating oil. These tanks typically have a lifespan of around 20-25 years but can last longer with proper maintenance and depending on factors such as construction, material, installation system, and soil condition. Regular inspections and preventative maintenance are crucial for extending the life expectancy of underground fuel tanks.
Leak detection in underground tanks is more challenging than in above-ground tanks, and leaks can have severe environmental consequences. Therefore, proactive measures and regular inspections by experts are essential to prevent costly and harmful fuel leaks. Some signs of potential issues with underground fuel tanks include dying plants nearby, soil staining, strong oil odours, rainbow sheen on puddled water, insect infestations, or unexpected changes in oil consumption.
In summary, while gasoline can sit for days in an underground tank, it is important to ensure that these tanks are properly maintained and monitored to prevent leaks and environmental contamination.
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Temperature-compensated gas pumps show volume at 15°C
When it comes to maximising your mileage, it is important to consider the temperature of the fuel you are putting in your car. This is because fuel expands when it is hot and contracts when it is cold. This means that if you fill up your car with warmer fuel, you are getting marginally less fuel than if you had filled up with cooler fuel.
To address this issue, many gas pumps now have built-in temperature compensation mechanisms. These mechanisms ensure that the volume of fuel dispensed is "volume corrected" to a standard temperature of 15°C, also known as V15. This means that regardless of the actual temperature of the fuel, the pump will calculate and display the volume of fuel you are receiving as if it were at 15°C. This allows for more accurate measurements and helps to eliminate temperature-related losses or gains for retailers.
For example, if a retailer purchases fuel at V15 and sells it at 11°C, the delivered fuel will adapt to the temperature in the tank, resulting in a decrease in volume. With temperature compensation, the retailer can recalculate the dispensing volume back to the accepted standard of 15°C, ensuring they receive the full volume they paid for.
It is worth noting that the temperature compensation mechanism in gas pumps may measure temperature either outside at pump level or underground at tank level. This can impact the accuracy of your mileage measurements, especially if you are fine-tuning the calibration of your Scangauge to match the volume-corrected temperature.
In conclusion, while temperature-compensated gas pumps displaying volume at 15°C can help improve accuracy and eliminate losses for retailers, it is not a significant enough factor to change your schedule or routine in chasing costs.
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Frequently asked questions
The best time to fuel your car is when your vehicle is low on fuel. There is a theory that fuelling your car at night or in the early morning when the temperature is cooler means you get more fuel for your money. This is because fuel expands when heated, so when it is cooler, the fuel is denser and you get more of it. However, most fuel stations store their fuel underground, where the temperature is constant throughout the day.
Yes, fuel does expand when heated, making the liquid less dense.
Not necessarily. While fuel does expand and contract with temperature changes, the difference in volume is minimal and unlikely to make a difference to your wallet. For example, a 15-degree temperature difference would result in a 1% gain in volume, which would only be a few cents' difference.
No, not really. The temperature in the tanks at the gas station can change when they are refilled from a tank truck, but as you don't know when this will be, you can't plan around it.
Yes, the fuel sitting in the pump dispenser can be warmed by the sun, so you may get marginally more fuel if you fill up when the dispenser is cooler.
