E15 vs E10: Which Should You Actually Buy?
For most drivers with a 2001 or newer car, E15 (Unleaded 88) is the better buy: it costs less per gallon than E10 and loses only about 1 to 2% fuel economy, so the discount wins. The catch is eligibility. E10 works in every gasoline car, while E15 is federally approved only for 2001 and newer light-duty vehicles. If your car qualifies and the station near you sells it, pick E15. If your car is older, or you drive a motorcycle, boat, or mower, stick with E10.
What the Two Fuels Actually Are
E10 is regular gasoline with up to 10% ethanol. It is the default fuel at nearly every US pump and is approved for all conventional gasoline vehicles.
E15 is gasoline with up to 15% ethanol. It is sold under the retail name Unleaded 88, because the blend usually carries an 88 octane rating, one point higher than regular 87. The “88” is the octane number, not the ethanol percentage, which is the source of most of the confusion at the pump.
Price: E15 Wins Per Gallon
E15 is almost always cheaper per gallon than E10 at the same station. Minnesota’s Department of Commerce reported that Unleaded 88 averaged 13 cents per gallon less than regular unleaded in 2025, and industry surveys put typical savings at 10 to 30 cents per gallon. Discounts vary by state and station, and some analysts note the spread could shrink if E15 becomes widely available, but today the price edge is real.
E15 costs less because ethanol is cheaper than the gasoline it replaces, and a higher ethanol blend simply contains less petroleum.
Mileage: E10 Wins, but Barely
Ethanol holds about 33% less energy per gallon than gasoline, so more ethanol means slightly fewer miles per gallon. E15 delivers roughly 1 to 2% lower fuel economy than E10, according to industry data, and many drivers cannot detect the difference at all.
Do the math and the verdict is clear: a 1 to 2% mileage loss cannot erase a 10 to 30 cent per gallon discount. Unlike E85, whose 15 to 25% mileage penalty can wipe out its cheaper pump price, E15’s tiny energy deficit loses to its price advantage in almost every case.
Octane and Performance
E15’s extra octane is a genuine benefit. At 88 octane, it resists engine knock slightly better than 87 octane E10, which can help engines run at their best timing, especially small turbocharged engines that are sensitive to knock. You will not feel more power, but the fuel is objectively higher grade on the knock-resistance scale.
Compatibility: The Deciding Factor
| Question | E10 | E15 |
|---|---|---|
| Approved for all gasoline cars? | Yes | No, 2001 and newer only |
| Motorcycles? | Yes | No, federal prohibition |
| Boats and marine engines? | Yes | No, federal prohibition |
| Lawnmowers and small engines? | Yes | No, federal prohibition |
| Typical octane | 87 | 88 |
| Price per gallon | Baseline | Usually 10 to 30 cents less |
| Fuel economy | Baseline | About 1 to 2% lower |
E15 was approved by the EPA in 2011 after the EPA and DOE tested it in 80 vehicles for more than 6 million miles. But the approval covers only 2001 and newer light-duty vehicles and flex-fuel vehicles. Motorcycles, boats, off-road engines, and pre-2001 cars are federally prohibited from using it, and misfueling can violate the Clean Air Act.
One more caution: the model year is the starting point, not the whole answer. Some automakers limit certain engines to E10 in the owner’s manual. If your manual says E10 only, follow the manual regardless of the model year.
Availability: E10 Is Everywhere, E15 Is Growing
E10 is at virtually every gas station in America. E15 is at roughly 4,600 stations and counting (Renewable Fuels Association, end of 2025), concentrated in the Midwest: Iowa, Minnesota, Illinois, Nebraska, and Wisconsin. Chains like Sheetz, Casey’s, Kwik Trip, QuikTrip, and Murphy USA sell it, usually at blender pumps alongside E85. Availability is thinner on the coasts. You can find stations on our E15 gas station guide, and if you need fuel with zero ethanol, see our ethanol-free gas station guide.
The Bottom Line
Choose E15 if your car is a 2001 or newer gasoline vehicle (or any flex-fuel vehicle), your owner’s manual allows it, and a station near you sells it. You will pay less per gallon, lose almost nothing in mileage, and get slightly higher octane.
Choose E10 if your car is older than 2001, your manual limits you to E10, you ride a motorcycle, or no station near you offers E15. It remains an excellent, safe default for everything. Looking to save on regular fill-ups? Check our cheap gas guide for more ways to pay less per tank.
FAQs
Can I mix E15 and E10 in the same tank?
Yes, if your vehicle is approved for E15. Blending the two just gives you something in between, like E12. Your engine will not know the difference.
Is Unleaded 88 the same as E15?
Yes. Unleaded 88 is the retail name for E15, named for its 88 octane rating. Look for the EPA’s orange-and-black E15 label on the dispenser to confirm.
Will E15 void my car warranty?
It should not, as long as your owner’s manual approves it. All major automakers certify their 2012 and newer vehicles for E15. Check your manual first, because that document controls warranty coverage.
Is E15 better for the environment than E10?
Slightly. The extra ethanol displaces more petroleum and cuts tailpipe emissions modestly. The difference is small but real, and it is one more reason the fuel is growing at Midwest pumps.
Facts verified October 2026. Station counts and prices vary by state and change over time.