Why did the break-even point move from 70% to 73%?

In August 2025 Brazil raised the ethanol content in regular gasoline to E30, which slightly changed the relative energy efficiency between the two fuels. The old 70% figure, based on the previous blend, now under-recommends ethanol.

Does my car's fuel economy change the answer?

Yes. The break-even percentage is a national average across flex engines. If you know your own car's real-world km/L on ethanol and gasoline, entering those numbers gives a more accurate verdict than the generic ratio alone.

Is ethanol always cheaper than gasoline per liter?

The price per liter is usually lower, but ethanol also delivers fewer kilometers per liter. That's why comparing raw prices is misleading — the price ratio against the break-even threshold is what actually determines the cheaper fuel.

Does the 70-73% rule apply to E85 flex-fuel vehicles outside Brazil?

The same logic applies, but the exact threshold differs — US E85 vehicles typically see a larger fuel-economy penalty than Brazilian flex engines, so the break-even ratio is often higher. Use the adjustable slider to set the threshold that matches your own vehicle.

How do I calculate cost per mile for E85 vs gasoline?

Divide each fuel's price by your vehicle's real fuel economy on that fuel — this calculator does that automatically once you fill in the optional consumption fields, showing cost per kilometer for both fuels side by side.

Ethanol vs Gasoline Calculator

Free ethanol vs gasoline calculator: find which fuel is cheaper per km with the 70% break-even rule. Compare prices and cost per kilometer instantly.

Updated June 2026

Ethanol vs Gasoline

70% Rule

Ethanol Price

Gasoline Price

Ethanol economy (km/L)

Gasoline economy (km/L)

Technical Note: Ethanol delivers about 70% of gasoline's energy per liter, so it only pays off when its price is below the break-even point. With Brazil's E30 gasoline (since Aug/2025) the threshold rises to ~73%.

Verdict

Essentially tied

0% 100%

Price ratio: 72.7%

Ethanol cost/km

$0.094

Gasoline cost/km

$0.092

How the ethanol vs gasoline calculator works

Two prices in, one clear verdict out

1. Enter both fuel prices

Type the price per liter (or gallon) of ethanol and gasoline at the pump you actually use — the comparison only makes sense when both come from the same station and the same visit.

2. Adjust for your car's real fuel economy (optional)

Add your vehicle's actual km/L on each fuel for a sharper answer than the generic break-even percentage alone.

3. Read the verdict

The calculator divides the two prices, compares the ratio to the break-even threshold, and tells you which fuel is the better deal right now.

What this ethanol vs gasoline calculator does

Built on the current break-even math, not the outdated rule of thumb

Updated 73% break-even threshold

Defaults to ~73%, reflecting Brazil's current E30 gasoline blend (in effect since August 2025) — many older calculators still use the outdated 70% rule.

Adjustable for any flex-fuel setup

Drag the threshold anywhere from 60% to 85%, with one-click presets for the classic 70% rule and the current 73% figure, so it fits ethanol blends and E85 flex-fuel vehicles outside Brazil too.

A straight answer, no mental math

Get a plain verdict — ethanol, gasoline, or essentially tied — instead of doing division at the pump.

Cost-per-km breakdown

Once you add fuel economy for both fuels, see the actual cost per kilometer for each side by side, not just the price ratio.

Example scenarios

How the price ratio decides the verdict

Prices (ethanol / gasoline)

Verdict

$2.80 / $4.00 (70% ratio)

Below 73% → ethanol is the better deal

$3.10 / $4.00 (77.5% ratio)

Above 73% → gasoline is the better deal

$2.92 / $4.00 (73% ratio)

Right at the threshold → essentially tied

$3.20 / $4.20 (76% ratio, custom 80% threshold)

Below your custom threshold → ethanol still wins

When you'll reach for this calculator

The situations flex-fuel drivers run into most

Daily fill-ups

Decide which pump to choose in seconds by comparing the prices posted right in front of you.

Long road trips

Work out which fuel will actually cost less over the whole trip once your car's real fuel economy is factored in.

Comparing gas stations

Check whether it's worth driving to a different station based on how its ethanol and gasoline prices compare to your usual spot.

Rideshare and delivery drivers

Cut cost per kilometer over a full month of driving by consistently picking whichever fuel comes out ahead.

Common mistake? Start here

Relying on the old 70% rule

Since Brazil's gasoline blend moved to E30 in August 2025, the break-even point sits closer to 73% — a calculator still using 70% will steer you toward gasoline more often than it should.

Ignoring your car's real fuel economy

The generic percentage is an average across flex engines; your specific engine may get noticeably better or worse mileage on ethanol, which can flip the verdict.

Mixing prices from different stations or days

The comparison only holds if both prices come from the same pump at the same time — fuel prices shift daily and vary a lot between stations.

Why use this ethanol vs gasoline calculator

It defaults to the current ~73% break-even ratio for Brazil's E30 gasoline instead of the outdated 70% rule that most free calculators still ship with, so the verdict actually matches today's fuel blend.

The threshold is fully adjustable from 60% to 85%, so drivers of other flex-fuel or E85 vehicles can dial in the ratio that matches their own engine instead of trusting a one-size-fits-all percentage.

Frequently asked questions

Divide the ethanol price by the gasoline price. If the result is below roughly 73% (the current threshold for Brazil's E30 gasoline), ethanol is the cheaper fuel per kilometer driven. Above that line, gasoline wins.

Resources

Alternative Fuels Data Center — E85 (Flex Fuel)

U.S. Department of Energy reference on ethanol fuel, E85 blends, and flex-fuel vehicle compatibility.

fueleconomy.gov — Flex-Fuel Vehicles

Official U.S. government comparison of fuel economy and cost between E85 and regular gasoline in flex-fuel vehicles.

Ethanol fuel — Wikipedia

Background on ethanol as a vehicle fuel, including energy content, blends, and use around the world.