Fuel Cost and Ethanol vs Gasoline
Work out the fuel cost of a trip, split it among passengers and check whether ethanol or gasoline is cheaper for a flex-fuel car.
Brazil: ethanol or gasoline?
Flex-fuel cars run on ethanol, gasoline or any mix. Ethanol is cheaper per liter but the car goes fewer kilometers with it, so compare the prices at the pump.
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Frequently asked questions about fuel costs
How do I convert MPG to L/100 km?
Divide 235.21 by the US MPG figure, or 282.48 by the UK MPG figure. A car doing 30 MPG (US) uses about 7.84 L/100 km.
What is the difference between MPG (US) and MPG (UK)?
The UK (imperial) gallon holds 4.546 liters and the US gallon 3.785 liters, so the same car shows a higher MPG figure in the UK.
Is the 70% rule always right?
No. It is an average: some engines do better or worse with ethanol. Measure how many kilometers your car does per liter with each fuel and use the comparison by consumption.
Does the trip cost include tolls and wear?
No. The calculator covers fuel only; tolls, parking, tires and maintenance are extra.
How the fuel cost calculator works
This calculator tells you how much fuel a trip needs and what it costs. Enter the distance in kilometers or miles, the consumption of the vehicle in km/L, L/100 km, MPG (US) or MPG (UK), and the fuel price per liter, per US gallon or per UK (imperial) gallon. You can double the distance for a round trip and split the bill among the people sharing the ride. A second form is for Brazilian drivers with a flex-fuel car: it compares ethanol and gasoline prices at the pump and tells you which one to use. It suits drivers planning a trip, friends sharing a ride and anyone standing at the pump.
Everything is converted to liters and kilometers with exact factors: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L and 1 UK gallon = 4.54609 L. Fuel needed = distance × L/100 km ÷ 100, and the cost = fuel × price per liter. For ethanol against gasoline there are two checks. The 70% rule says ethanol pays off when its price is below 70% of the gasoline price. The more accurate check uses your own figures: cost per 100 km = price ÷ km/L × 100, and your break-even ratio = km/L with ethanol ÷ km/L with gasoline.
Example: a trip of 300 miles each way is a round trip of 600 miles. At 30 MPG (US) it needs 20 US gallons, and at US$ 3.50 a gallon the trip costs US$ 70.00, or US$ 35.00 each for 2 people. In Brazil, with ethanol at R$ 4.19 and gasoline at R$ 6.29 the ratio is 66.61%, so ethanol pays off. With 8.4 and 12.1 km/L, ethanol costs R$ 49.88 per 100 km against R$ 51.98 for gasoline. Real consumption varies with speed, load, traffic and air conditioning, and tolls are not included.