What Gas Costs and Why · Published · Updated
Canadian motorists buy fuel in Canadian dollars, but international crude benchmarks are usually quoted in US dollars. That creates a second moving part between the oil-market headline and the number on the station sign. Even if the US dollar price of oil is unchanged, its Canadian dollar equivalent can rise or fall. Understanding that conversion helps explain why a story about cheaper oil does not always produce an immediate, equally sized saving at the pump.
The latest Canadian gasoline observation in this site's data release is CAD 1.87 per litre (2026-09-15). That price includes more than crude. Taxes, refining, distribution and retail conditions also matter. Currency is one part of the explanation, and isolating it requires holding other inputs constant. The following examples are deliberately hypothetical so the arithmetic is easy to inspect and is not mistaken for a current forecast.
Follow the direction of the exchange rate
Suppose oil costs US$80 per barrel and one US dollar buys C$1.35. The Canadian dollar cost is 80 multiplied by 1.35, or C$108 per barrel. If the exchange rate moves to C$1.40 per US dollar with oil still at US$80, the barrel costs C$112. The US dollar oil price has not changed, but the Canadian cost has risen by C$4.
Dividing the C$4 difference by 158.987 litres per barrel produces roughly C$0.025 per litre of crude allocation. That is about 2.5 Canadian cents per litre. It is not a promise that every station will raise gasoline by exactly that amount. The calculation measures the direct conversion effect on an assumed crude allocation, before the other components of the pump price respond.
People often reverse the exchange-rate quotation accidentally. If the rate is Canadian dollars per US dollar, you multiply a US dollar amount to obtain Canadian dollars. If it is US dollars per Canadian dollar, you divide instead. A useful check is to ask whether the answer moves in the expected direction: when the Canadian dollar weakens, the same US dollar purchase should cost more Canadian dollars.
Oil and currency can move together
Now suppose oil falls from US$80 to US$76 while the exchange rate moves from C$1.35 to C$1.40 per US dollar. The original local cost was C$108. The new one is C$106.40. Oil fell 5% in US dollars, yet the local barrel cost fell by only about 1.5%. Currency offset much of the decline. Looking only at the oil headline would overstate the expected relief in the local crude component.
The opposite combination is also possible. If oil rises but the Canadian dollar strengthens, the currency move can soften the increase. If both move against the buyer, they can amplify each other. These examples do not imply a dependable trading relationship between oil and the Canadian dollar. They simply show why two observed variables belong in the calculation rather than one.
A percentage change in crude is also not the same percentage change in the complete pump price. If crude accounts for only part of the total, its movement is diluted when expressed against the whole litre. Other components can move in different directions. This distinction matters when checking a claim that a particular percentage fall in oil should produce the same percentage fall in gasoline.
What a currency-effect field can tell you
A useful way to isolate currency is to calculate the crude allocation twice. First use the current oil price and current exchange rate. Then use the same oil price with the previous week's exchange rate. Subtract the second result from the first. Holding oil constant makes the difference an estimate of the direct exchange-rate effect within that calculation.
This method is a comparison against an alternative scenario. It does not observe a separate currency charge paid at the pump. A retailer does not necessarily receive a bill labelled foreign-exchange effect. Contracts, inventory timing and financial arrangements can delay or change how exchange-rate movements appear in product prices. The field explains the model's sensitivity, not the exact cash flow of a business.
The Bank of Canada Valet service supplies reference-rate data suitable for transparent calculations. The source and the date still matter. A reference rate is not necessarily the rate a company receives on a transaction, and a daily rate is not a forecast. On this site, the relevant rate must have been available on or before the price observation.
Why a station may move later
Fuel sold today may have been purchased earlier. Different stages in the supply chain can turn over inventory at different speeds. A crude-price movement may appear in wholesale products before it is reflected in a particular retail survey. Stations also compete locally, so neighbouring sellers can respond at different times. A delay alone does not establish that a currency calculation is wrong or that a retailer is retaining a particular amount.
A better comparison uses several observations rather than one day. Check the dates of the crude benchmark, exchange rate and retail series. Ask whether the fuel is gasoline or diesel and whether a refinery disruption has changed the product market. Currency can be an important contributor while still being smaller than a change in the downstream component during an unusual supply event.
Taxes can change the final arithmetic
Some taxes are fixed amounts per litre, while others are percentages of a taxable price. A fixed duty does not mechanically increase when the Canadian dollar weakens. A percentage tax can rise when the underlying taxable price rises. The final currency-related change in a tax-inclusive price therefore depends on which taxes apply and how their bases are defined.
This is why a national comparison should not use Vancouver's local levy as if it applied throughout British Columbia, or a provincial rate as if it described every Canadian city. The Canadian regional pages keep geography visible. The fuel-tax records distinguish the federal policy schedule from the province-specific details that still require verification.
Use currency as a disciplined question
When the pump price surprises you, ask whether oil changed in US dollars, whether the Canadian dollar changed, and whether the pretax downstream portion changed. Then examine tax policy separately. That sequence is more informative than choosing one cause from a headline. It also helps identify what additional evidence would be needed to explain a particular week.
A currency conversion is precise arithmetic applied to selected inputs. Its precision should not be mistaken for certainty about the entire fuel market. The useful result is a clear, reproducible estimate of one mechanism. Combined with dated retail observations and honest limits, it explains how the Canadian dollar can influence the price without claiming to predict the next station update.