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Does the weather affect your bill at the pumps?


Natalie Thomas, reporter
March 9, 2012 — Can filling up your car in the morning save you money at the pumps? The Weather Network put this theory to the test


It's safe to say this urban legend is based on scientific fact
It's safe to say this urban legend is based on scientific fact

There is an idea floating around on the internet that suggests filling up your tank with gasoline in the morning when temperatures are at their coolest, as opposed to the afternoon when it gets warmer.

So we decided to put this theory to the test: can filling up your car in the morning save you money at the pumps? "Well that notion is based on really the science of liquids and densities," says Dayna Vettese, a meteorologist at The Weather Network.

"When we have liquids such as gasoline in a colder state, it tends to be denser. †But when it warms up we tend to get a less dense state of the liquid." † ††

So it is safe to say this urban legend is based on scientific fact.†However, even though this theory might have been true 40 years ago, Automatic Temperature Compensation has changed that.†ATC is essentially a process that corrects the volume of liquids (in this case, gasoline or diesel) to compensate for temperature fluctuation.†Here in Canada, †gasoline volume is corrected to 15 degrees Celsius.

"Fifteen degrees is an international standard," says Tricia Anderson, President and CEO of the Canadian Independent Petroleum Marketers Association (CIPMA).†"That standard has been used for decades in the wholesale business, in international product exchanges, and in marine shipments.†So it just made sense when this was introduced at the retail level to use a universal standard."

Itís a fair process, no matter if it's summer or winter
Itís a fair process, no matter if it's summer or winter

It may be the universal standard, but it appears to mirror the American climate as opposed to our own.

"In the continental United States," Vettese tells us, "after averaging a few of the major cities we see that the average annual temperature is about 15 degrees Celsius.†Here in Canada when averaging a few of our major cities we see that the average annual temperature is only about 5 degrees."†

No matter what the standard is, it is used across the board.†Anderson tells us that almost all pumps manufactured in the last 20 to 25 years have ATC embedded in the system.†Those pumps are easily identified as they have stickers on them, indicating that the fuel is being temperature corrected and temperature compensated as it is being dispensed.†

"So to make sure weíre dispensing accurately, pumps in Canada for the last, well over 20 years, have been actually compensating for these temperature changes so thereís accurately in the dispensing," Anderson explains.†"Itís a fair process and no matter if it's summer or winter, whatever the temperature, youíre getting a litre thatís been corrected to the same temperature.†So that makes sense for all parties, itís a fair process."†

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