Fuel Cost Calculator

Fuel is often the largest running cost of a road trip, and it is easy to estimate in advance. For the default example, a 500-mile trip in a car that averages 25 mpg uses 20 gallons; at $3 a gallon that is $60. Use your car's real-world mileage if you know it, since window-sticker figures can be optimistic, and allow a margin for city driving, hills, headwinds, a loaded car or air conditioning. Splitting the result by the number of passengers gives each person's share.

There are two ways to bring the bill down: use less fuel, and pay less for the fuel you buy. The tips below cover the first; the sections after them explain what drives the price at the pump.

Formula

Fuel cost = distance ÷ fuel efficiency × price per unit of fuel

With L/100 km: cost = distance (km) × L/100 km ÷ 100 × price per liter.

Use public transportation

Buses, trains and subways carry many people per vehicle, so the fuel or electricity used per passenger is a fraction of a solo car trip. For a daily commute the savings in fuel, parking and wear on the car can amount to thousands of dollars a year, and many employers offer pre-tax transit benefits that stretch the savings further.

Carpool

Sharing a ride splits the fuel cost among everyone in the car and takes vehicles off the road. Many regions also give carpools access to faster high-occupancy vehicle lanes, which cuts time spent idling in traffic.

Use a more fuel efficient vehicle

When you replace a car, fuel economy has a lasting effect on running costs. Going from 20 mpg to 30 mpg cuts fuel use by a third. Hybrids excel in city driving, and electric vehicles avoid gasoline entirely. Households with two cars can use the more efficient one for long trips.

Tune the engine

A well-maintained engine burns fuel more completely. Follow the service schedule in the owner's manual: replace the air filter and spark plugs at the recommended intervals, and do not ignore a check-engine light, which can signal a faulty oxygen sensor or misfire that wastes a surprising amount of fuel. Fuel-system cleaning is rarely needed on modern cars that use quality gasoline.

Avoid aftermarket gadgets that promise big mileage gains; the US Environmental Protection Agency has tested many such devices and found little or no benefit. The cheapest improvements are routine maintenance and smoother driving.

Adjust tires

Tires inflated below the recommended pressure flex more as they roll, which increases rolling resistance and fuel use and shortens tread life. Check pressures at least monthly with the tires cold and inflate them to the value on the sticker inside the driver's door, not the maximum molded into the sidewall. Pressure drops about 1 psi for every 10 °F fall in temperature, so check more often as the weather turns cold.

Correct wheel alignment also matters: wheels that point slightly in different directions scrub against the road. Low-rolling-resistance tires, available for most cars, can improve economy by a few percent when it is time for replacements.

Use the correct motor oil

Use the viscosity grade the manufacturer specifies, such as 0W-20. Thicker oil than recommended increases internal friction and can lower fuel economy by 1% to 2%. Look for oil labeled Resource Conserving, which indicates friction-reducing additives.

Plan trips carefully

Combine errands into one outing, since a warm engine is far more efficient than a cold one. Choose routes that avoid congestion and long climbs where practical, travel outside rush hour if you can, and use navigation apps to dodge traffic jams. On long trips, apps that compare local fuel prices can save several cents per gallon, and filling up before entering expensive areas such as city centers, airports or highway service plazas helps too.

Factors that determine the fuel price

The price at the pump bundles the cost of crude oil, refining it into gasoline or diesel, distributing and selling the fuel, and taxes. The US Energy Information Administration publishes a monthly breakdown; crude oil is normally the largest share, followed by refining, taxes and distribution. Several forces move those components.

Government intervention

Governments add fuel taxes and set rules on fuel formulas. In the United States the federal gasoline tax is 18.4 cents per gallon and each state adds its own, so prices vary noticeably across state lines. Many European countries tax fuel far more heavily. Governments can also release strategic reserves, set price caps or offer subsidies.

Financial markets

Crude oil and refined fuels trade on futures markets, so expectations about supply, demand, interest rates and the value of the dollar move prices before a barrel changes hands.

Politics

Much of the world's oil comes from a small number of countries, and decisions by producer groups such as OPEC and its allies to raise or cut output have a direct effect on crude prices. Wars, sanctions and unrest in producing regions or along shipping routes can lift prices quickly, even when actual supply is barely affected, because traders price in the risk of disruption.

Geographic area

Where you buy matters. Areas close to refineries and pipelines tend to have cheaper fuel, while remote places pay more for transport. Some regions require special cleaner-burning blends that cost more to make, and local competition, rent and wages at the station also feed into the price.

Natural disaster or weather

Hurricanes, floods and extreme cold can shut down offshore platforms, refineries and pipelines, and prices can jump within days, as happened along the US Gulf Coast after major hurricanes. Demand also follows the seasons: prices usually rise in spring and summer as driving increases and refiners switch to more expensive summer-grade gasoline, and ease in the autumn. The table shows the usual shares of the retail price of regular gasoline in the United States.

Frequently asked questions

Sources

• US Department of Energy – fueleconomy.gov
• US Energy Information Administration