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1999-03-01 Automatic Temperature Compensation and the Retail Sale of Gasoline and Diesel Fuel

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Industry Canada has prepared some answers to the question: How does automatic temperature compensation affect the sale of gasoline and diesel fuel?

What is an automatic temperature compensator?

An automatic temperature compensator is an electronic device which measures the temperature of petroleum products during delivery and automatically calculates the amount of product as though it had been delivered at 15°C. This practice is known as automatic temperature compensation (ATC).

How does temperature compensation affect the way I buy gasoline?

The laws of physics dictate that the volume of a given mass will vary depending on its temperature but that the amount of energy in that mass will not. ATCs calculate the volume of fuel at a constant temperature instead of the old method of volume at the temperature of the product. ATC means that, for the same grade of fuel, no matter what the fuel temperature, consumers receive the same amount of energy per litre.

Why is the amount of energy important?

Although gasoline is purchased by volume, and people discuss vehicle mileage on the basis of volume, it is actually the energy contained in the gasoline which makes vehicles function.

Why was 15°C chosen as the reference temperature for ATC?

The reference temperature of 15°C is a long-standing international standard used in all countries for the purchase and sale of petroleum products. It has been used in Canada for other fuels (e.g. natural gas and propane) for decades. 

Would using a different reference temperature save me money?

No. The actual reference temperature used does not matter. In the sale of temperature compensated petroleum products, the volume is based on 15°C. This means that the consumer is paying for a 15°C litre at a 15°C price, no matter what the temperature of the product. If a different reference temperature were chosen, the purchaser would still receive consistent amounts of energy per litre. However, a different price per litre would be charged for fuel measured to a different reference temperature.

Is temperature compensation new?

Temperature compensation has been used in applications such as pipelines, ship-loading and tank farm transfers for decades. Prior to the advent of modern electronics, there was no way to perform this function accurately in retail dispensers.

In 1984, a Canadian electronics manufacturer designed a device which could readily measure the temperature of liquids and perform the necessary calculations. The device was submitted to and approved for use in trade by Measurement Canada¹. To date, about 70% of dispensers use the technology. A dispenser equipped with ATC can be identified by a sticker on the register which says "Volume Corrected to 15°C".

Do retailers benefit from the use of ATC?

Retailers purchase gasoline from their suppliers on a temperature compensated basis. The use of temperature compensation to a common reference temperature allows retailers to sell product on the same basis as it was purchased. This common basis of measurement eases the reconciliation of product inventories and permits the early detection of smaller leaks from storage.

Do consumers benefit from the use of ATC?

Consumers benefit from the knowledge that temperature compensation is a more accurate system of measurement which ensures that the amount of energy they purchase is not affected by the temperature of the fuel. ATC allows consumers to make meaningful price comparisons between retailers. Posted prices at non-ATC equipped retailers can be misleading because of variation in product temperatures.

Is ATC used in other applications?

Yes. The use of ATC is mandatory in Canada for the sale of natural gas and propane. Its use is optional in the sale of gasoline and diesel because the volume of the latter two fuels changes relatively less with temperature.

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¹    Measurement Canada is responsible for the approval and inspection of all weighing and measuring devices, to protect consumers, and to ensure efficient functioning of the marketplace in Canada. For a particular measurement system to be used in trade, it must first receive approval as required by federal legislation. This begins with a laboratory evaluation to ensure that the system complies with applicable requirements for performance, design, composition and construction. Once the pattern has been approved, each new device is inspected prior to use to ensure that it is installed correctly and that it measures within specified tolerances. Subsequent inspections are conducted to ensure that the device continues to measure accurately and is not used in a manner that may lead to errors.

Our motto is "Fair measure for all".