Premium gas usually costs noticeably more per gallon than regular. Whether that's money well spent depends on one line in your owner's manual. This calculator shows what premium costs you per fill-up, per month and per year, so you can decide with real numbers.
How it's calculated
- Gallons per year = miles per year ÷ MPG.
- Extra cost per year = gallons per year × (premium price − regular price).
- Extra per fill-up = tank size × price gap.
At 12,000 miles a year and 28 mpg, you buy about 429 gallons a year. An 80-cent gap costs about $343 a year.
Required, recommended, or neither?
Your owner's manual, and often a label inside the fuel door, says which applies to your engine:
| What the manual says | What it means |
|---|---|
| Premium required | Use premium. Lower octane can cause knocking and, over time, engine damage, and may affect warranty coverage. |
| Premium recommended | Regular is acceptable. The engine adjusts its timing; you may lose a little power and fuel economy. |
| Regular (87) | Premium brings no benefit in normal driving. |
- Premium required
- What it means
- Use premium. Lower octane can cause knocking and, over time, engine damage, and may affect warranty coverage.
- Premium recommended
- What it means
- Regular is acceptable. The engine adjusts its timing; you may lose a little power and fuel economy.
- Regular (87)
- What it means
- Premium brings no benefit in normal driving.
Octane is a measure of resistance to knock (early ignition), not of energy content or cleanliness. Most stations sell regular at 87 and premium at 91 to 93 in the US. At high altitude, some stations sell lower-octane grades; follow your manual.
Frequently asked questions
Is premium gas worth it?
Only when your manual requires it, or if you've tested "recommended" premium on your own car and the fuel-economy gain covers the price gap. Otherwise regular costs less for the same result.
Can I mix regular and premium?
Yes. Mixing grades in the tank just gives you an octane rating in between. If your car requires premium, avoid letting the mix fall too far.
What happens if I put regular in a premium-required car?
Modern engines use knock sensors to retard timing and protect themselves, so a single tank is unlikely to cause harm, but you may lose power and MPG. Go back to premium at the next fill-up, and avoid it as a habit.
Does premium improve MPG?
In engines designed for regular, no. In engines that recommend premium, gains are usually small. Measure it yourself over several tanks with the MPG calculator.
Results are estimates from the numbers you enter and, where noted, EPA ratings. Not financial advice. Page updated .