Two fuel prices can look comparable while describing different purchases. One may be for another grade, another unit, or a payment condition you will not use. A fair budget experiment begins by matching those details—not by choosing the smallest number on the sign.

Create My Piggy in your browser to set a manual transport target and compare it with spending you explicitly record. No account or app download is required. For a separate price-only experiment, open the fuel calculator and replace its default prices with the fictional inputs below.

First match the fuel your vehicle requires

The U.S. Department of Energy and EPA's FuelEconomy.gov guidance says to follow the vehicle manufacturer's octane requirement and check the owner's manual. We checked that undated guidance on October 23, 2026. This article is not a recommendation to switch to a lower grade. A regular-price sign and a premium receipt do not establish a like-for-like price change.

For your comparison, write down the fuel type, required grade, volume unit, date and payment condition. Keep the same formulation where relevant. Do not compare a price per litre with one per U.S. gallon by changing the calculator's unit label; that performs no conversion.

Make the payment conditions explicit

Check the price you can actually use, including applicable fuel taxes and any condition needed for the advertised discount. A cash price, card price and membership offer are three different conditions until you establish otherwise. Do not assume an unverified station offers any particular discount.

If a price requires a paid membership, transaction fee, minimum purchase or an extra trip, record that separately. The calculator below compares only per-unit prices at a fixed quantity and frequency. It does not automatically subtract membership charges, card rewards or detour costs, and it does not establish which payment method is best for you.

A fictional 20-cent difference, checked

Assume an October 23, 2026 USD planning example for the identical manufacturer-compatible gasoline grade and formulation. Both prices are per U.S. gallon and include any applicable pump taxes. Suppose option A is USD 5.00 and option B is USD 5.20, with no membership charge, transaction fee, reward, coupon, extra travel or other discount. These are invented inputs, not verified station prices.

At 12 U.S. gallons per purchase and one purchase weekly, option A costs 5.00 × 12 = USD 60.00 per purchase; option B costs 5.20 × 12 = USD 62.40. The difference is USD 2.40 weekly. If that exact routine continued for 52 weeks, the projected difference would be USD 124.80 annually, or USD 10.40 per average month. It is not actual savings, a fuel-price forecast or the exact cost of your next calendar month.

Use the supported comparison—not an automatic winner

In the fuel-rise preset choose USD, U.S. gallon, previous price 5.00, scenario price 5.20, quantity 12, frequency one and repeat period Week. Confirm compatibility only after checking the grade, unit and tax/discount basis. Expected results are USD 2.40 more weekly, USD 10.40 more per average month and USD 124.80 more annually.

Here, previous and scenario are input labels; the example does not establish a historical price rise. Switching the inputs reverses the sign. If your weekly gallons change, this is a different experiment: the single quantity input is shared by both prices. If you cannot establish comparable conditions, leave the compatibility box unchecked rather than treating uncertainty as a zero difference.

Keep receipts and headlines in their own lanes

A receipt can help you check what one purchase cost, after reviewing its details. A partial set of receipts cannot establish all your driving, complete spending or income. Optional budget saving is browser-local, not cloud backup or native-app sync. The separate receipt-to-Excel scanner handles one selected photo per workbook and requires OCR review; the native iPhone app is separately coming soon.

National petroleum news does not settle this station comparison. Emergency SPR crude, commercial crude excluding SPR, refined gasoline or distillate stocks, and underground proved reserves are different measures. An announced exchange is not a daily inventory observation and does not guarantee a pump-price change. This guide reports no inventory figures and applies no fuel-to-food inflation multiplier.

Your takeaway: compare the purchase you would actually make

A useful comparison has matching fuel specifications, units and clearly stated payment assumptions. Once those match, the arithmetic is small enough to check—and the result describes only that experiment.

Try the fuel scenario with your own compatible inputs, then give transport a manual budget target. Change the plan if it helps; there is no need to turn a price comparison into a judgment about your routine.

Sources and coverage

Primary guidance supports following manufacturer fuel requirements. All prices, quantities and payment conditions in the worked example are fictional assumptions dated October23,2026. No company or station price, current inventory figure, reward entitlement or guaranteed saving is claimed.

A little clarity, not a guarantee

Projections are not recorded spending or confirmed savings. No national average or future price is inferred. The web calculator does not upload receipts, send family requests, or update the iPhone app.