Is cheaper gas worth the extra drive?
11 October 2026 · Groupe Sentinelle, developer of Sentinelle Auto. This is our own explanatory guide, not an independent app review.
To decide whether a cheaper gas station is worth the drive, subtract the cost of the extra fuel, tolls and other extra charges from the saving on the amount you plan to buy. Compare the same fuel grade and check the price timestamp before leaving.
US example: gallons, MPG and dollars
Suppose you plan to buy 12 US gallons and another station is $0.15 cheaper per gallon. The gross saving is $1.80. If reaching it adds 10 miles to your total journey and your car gets 30 miles per US gallon, you use about 0.333 extra gallons. At a fictional $3.60 per gallon, that costs $1.20. The fuel-only net saving is $0.60. An extra $1 toll makes the result a $0.40 loss.
These are invented teaching values, not current gas prices, measured app savings or a national average. Your time, parking and vehicle wear can reduce the benefit further.
Canada example: litres and cents per litre
A 4-cent-per-litre difference on 50 litres saves $2 before travel. An extra 10 km at 7 L/100 km uses 0.7 litres. At a fictional $1.80/L, the extra fuel costs $1.26 and leaves $0.74. Convert cents to dollars before multiplying: 4 cents is $0.04.
Use the full extra distance, including the return to your original route. Keep the same currency throughout; the calculator does not convert CAD to USD. US and imperial gallons are different units: the US mode uses US gallons and US MPG.
Nearest, cheapest and best value are different
The nearest station minimises distance. The lowest posted unit price may require a detour or membership. Best value depends on your fill-up size and actual extra cost. A small top-up can make the same detour less useful than a full tank.
Check the exact fuel grade, any membership condition, station opening hours and the timestamp of the specific price. A recent app refresh does not by itself mean the station reported a new price. An unavailable price is not evidence that the station has run out of fuel.
Try the calculation before you drive
Calculate the net saving from a gas-station detour or estimate your trip or monthly fuel budget. Enter your own distance, consumption and price. Results cover fuel and the extra charges you enter, not the complete cost of owning a car.
Sentinelle Auto helps compare the available station results on a phone. Canadian coverage and US coverage vary; a supported region does not mean every station has a price. Check Android and iPhone availability before trying to download.