Fuel and Emissions
Premium Fuel Break-Even Calculator
Calculate how much premium fuel can cost while matching regular fuel cost per mile. Use the octane grade required by the manufacturer regardless of a small cost difference.
Enter one vehicle measurement set
Keep units and reference points consistent before comparing the output with a specification or earlier measurement.
Before interpreting the answer
Calculate how much premium fuel can cost while matching regular fuel cost per mile — the comparison is meaningful only after its reference case is fixed.
Use the octane grade required by the manufacturer regardless of a small cost difference — that condition defines when premium break-even price is comparable with another result.
When the vehicle decision also requires you to estimate direct carbon dioxide produced during accumulated engine idling, calculate it independently with the Vehicle Idling Emissions.
Measurement basis and units
Regular fuel price. Price per gallon of regular fuel — for this measurement, keep currency, tax treatment, and pricing period consistent across the comparison.
Document Regular-fuel economy as economy measured on regular fuel — this means you should match the fuel quantity to the same distance, fill method, and operating period.
The Premium-fuel economy entry represents economy measured on premium fuel — before calculating, match the fuel quantity to the same distance, fill method, and operating period.
A related vehicle record may need to compare fuel use over the same distance at two measured or modeled cruising economies, a relationship covered by the Driving Speed Fuel Economy Comparison.
An example with recorded units
For a numerical demonstration, retain Regular fuel price = $3.45/gal, Regular-fuel economy = 25 mpg, and Premium-fuel economy = 26 mpg.
Substitution into the equation gives Premium break-even price = $3.59/gal, Allowable premium = $0.14/gal, and Economy improvement = 4.00%.
If the next task is to estimate usable driving range while retaining a chosen fuel reserve, continue with the Fuel Tank Range.
How the quantities interact
In “premium break-even price = regular price × premium MPG ÷ regular MPG,” the printed units define how each term is interpreted.
No term beyond regular fuel price, regular-fuel economy, and premium-fuel economy is introduced in “premium break-even price = regular price × premium MPG ÷ regular MPG.”
Premium break-even price answers “Calculate how much premium fuel can cost while matching regular fuel cost per mile.” The additional displays, Allowable premium and Economy improvement, are a different view of the same entered measurements.
Performance and knock protection are not represented by MPG alone — when that condition changes, compare separate calculator runs instead of blending the inputs.
Because use the octane grade required by the manufacturer regardless of a small cost difference, a disagreement between premium break-even price and an outside reference should trigger a review of regular fuel price and premium-fuel economy.
What requires independent verification
A change in regular-fuel economy is not isolated if another vehicle condition changed between the two cases — for regular-fuel economy, the page specifically expects economy measured on regular fuel.
Build another useful comparison to estimate the economy and fuel-use change associated with a roof rack or rooftop cargo with the Roof Rack Fuel Economy Penalty.
Clarifying the calculation
What measurement source fits Regular fuel price when it represents price per gallon of regular fuel?
Because regular fuel price represents price per gallon of regular fuel, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Use the octane grade required by the manufacturer regardless of a small cost difference” affect Premium break-even price?
The condition “Use the octane grade required by the manufacturer regardless of a small cost difference” is not corrected automatically by the numeric inputs, so create a separate premium fuel break-even case when it changes.
What assumption is expressed by “premium break-even price = regular price × premium MPG ÷ regular MPG”?
In “premium break-even price = regular price × premium MPG ÷ regular MPG,” regular fuel price and regular-fuel economy are treated as parts of one vehicle case.