Find your real km/l, the fuel cost of a trip, and whether ethanol or gasoline is the better buy today.
Measuring real consumption takes one simple discipline: fill the tank completely, drive, then fill it completely again and note both the kilometres travelled and the litres it took. Dividing distance by litres gives your true km/l — 480 km on 40 litres is 12 km/l, or about 8.3 litres per 100 km, the unit used in Europe. This measured figure is almost always lower than the manufacturer's number, because it includes your traffic, your air conditioning and your right foot.
With consumption in hand, the cost of any trip is straightforward: divide the distance by the km/l to get the litres you will burn, then multiply by the price per litre. A 300 km drive at 12 km/l with fuel at R$ 5.80 needs 25 litres and costs R$ 145, or R$ 0.48 per kilometre. That cost-per-kilometre figure is the one worth remembering — it turns any distance into money instantly, and it is the honest number to use when splitting travel costs or deciding between driving and other options.
The ethanol versus gasoline question is a single division. Ethanol carries less energy per litre, so a flex engine runs roughly 25% to 35% fewer kilometres on it; the popular shortcut is the 70% rule — if ethanol costs less than 70% of gasoline, it is the cheaper fuel. Ethanol at R$ 3.50 against gasoline at R$ 5.80 is a ratio of 0.603, or 60.3%, comfortably below the threshold, so ethanol wins. The tool always shows the ratio itself, not just the verdict, because 70% is an average: the real break-even point for your specific car sits somewhere between 65% and 75%, and the only way to know it is to measure the km/l of each fuel yourself. All calculations run in your browser — no prices, routes or numbers are sent anywhere.
Consumption = distance ÷ litres (km/l); litres per 100 km = 100 ÷ km/l. Trip cost = (distance ÷ km/l) × price per litre, and cost per km = trip cost ÷ distance. Fuel choice: ratio = ethanol price ÷ gasoline price — below 0.70 ethanol is cheaper, at 0.70 or above gasoline is.
Yes, as a rule of thumb: below 70% ethanol usually costs less per kilometre. The exact break-even depends on your engine, which typically runs 25% to 35% fewer kilometres on ethanol, so the real threshold ranges from about 65% to 75%.
Fill the tank to the brim, reset the trip meter, drive normally and fill it to the brim again. Divide the kilometres shown by the litres it took — that is your true km/l for those conditions.
Official numbers come from standardised laboratory cycles. City traffic, air conditioning, roof racks, low tyre pressure, extra weight and aggressive acceleration all reduce real-world consumption, often by 10% to 30%.
Double the distance before calculating, or double the resulting cost. The tool works with whatever distance you type, so 300 km entered means 300 km driven.
No. It never connects to the internet — you type the prices you saw at the pump, and everything is computed locally in your browser.
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