Fuel Savings Calculator
Compute trip cost and savings vs another vehicle (more/less efficient). Shows savings in $ and liters.
Fuel economy: cost per km = price per liter / km per liter
Comparing fuels really comes down to cost per kilometer: cost_km = price_liter / consumption_kmL. Say gasoline runs R$ 6.00/L in a car doing 13 km/L, that's R$ 0.46/km; ethanol at R$ 4.00/L in the same car at 9 km/L lands at R$ 0.44/km, so ethanol takes it. For flex cars there's the 70% rule: ethanol pays off once its price drops below 70% of gasoline, because a liter of ethanol carries about 70% of gasoline's energy. A few habits help on the driving side. Cruise around 80–90 km/h, the band where rolling resistance and aerodynamic drag balance out lowest. Go easy on the throttle and the brakes. Keep tires inflated, since a 0.2 bar drop pushes consumption up roughly 3%. Use the A/C with some judgment (5–15% extra on the highway, though still cheaper than open windows once drag kicks in), and remember that each extra 100 kg of weight costs about 5% in consumption.
Applications
Planning a road trip and weighing gasoline against ethanol, choosing between Uber and your own car, ride-share drivers sizing up which vehicle to use, a monthly commuting budget, or sizing up a hybrid or electric car, where cost per km usually sits well below an ICE vehicle.
FAQ
Does A/C really increase consumption? It does, by 5 to 15% more on the highway. But once you're past 80 km/h, open windows create so much drag that the A/C turns out to be the cheaper choice.
Why is the optimal speed 80–90 km/h? Slower than that and the engine is stuck working inefficiently in lower gears. Faster, and aerodynamic drag grows with the square of speed until it takes over.
How accurate is the 70% rule? For most flex cars it's a solid approximation, though real efficiency shifts from engine to engine. If you want the exact answer, run a full tank of each fuel and compare.
Related Tools
Heat Rate
Calculate the heat rate of a power plant, HR = 360000 ÷ η, dividing 360000 by the thermal efficiency in percent. The result, in kJ/kWh, is the fuel energy consumed to generate one kilowatt-hour of electricity — the inverse of efficiency expressed on an energy basis. It is the power-generation industry's standard metric: the lower the heat rate, the more efficient and economical the plant. A 40% efficiency equals 9000 kJ/kWh; modern combined-cycle plants reach ~6000 kJ/kWh. It lets you compare plants and estimate fuel use. Enter the thermal efficiency in percent.
Fuel Cost Calculator
Calculate the fuel cost of a trip: enter distance in km, vehicle consumption (km/L) and price per liter. See liters needed, total cost and cost per km. All in the browser.
Jet Fuel Burn Knots Liters Calculator
Computes total jet fuel burn in liters from average flow in kg per hour, ground speed in knots and route distance in nautical miles.
Low-cost vs Conventional Travel Savings
Shows savings from choosing low-cost travel (hostel, street food, public transport) over conventional.
Energy per Elevator Trip
Calculate the potential energy spent to raise a load, E = m·g·h, from the unbalanced mass m (net load after the counterweight, kg), gravity g and the lift height h (m). The result, in joules, is the minimum theoretical energy to hoist the load — a basis for estimating the elevator's electrical consumption and the energy-regeneration potential. Modern elevators with regenerative drives recover part of this energy on descent (when the counterweight descends with a light car), feeding it back to the grid. Actual consumption is higher, divided by the efficiency. Enter the unbalanced mass and the lift height.
Fuel Consumption (km/L)
Calculates average km/L from distance driven and liters refueled.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.