You pull up to the pump and see three choices: 87, 89, and 93. Most drivers pick based on price or habit — but do you know how much ethanol is in each grade? And does the ethanol content actually differ between regular and premium gas?
This guide gives you the straight facts: exact ethanol percentages, a clear comparison table, and what the difference really means for your engine and your oil change schedule.
Quick Answer
- 87 octane regular gas — up to 10% ethanol (E10) at most U.S. stations
- 93 octane premium gas — also up to 10% ethanol (E10) at most stations; some stations sell ethanol-free (E0) premium
- The octane rating and ethanol content are separate properties — premium gets its higher rating through additives, not less ethanol
What Is Ethanol and Why Is It in Gasoline?
Ethanol is a grain alcohol (the same type found in alcoholic beverages) produced mainly from corn in the United States. Congress mandated its blending into gasoline through the Renewable Fuel Standard (RFS), originally designed to:
- Reduce U.S. dependence on foreign oil
- Lower tailpipe greenhouse gas emissions
- Support domestic agriculture
- Boost octane — ethanol has an octane rating of about 113, which helps blenders hit the target octane number cheaply
Today, virtually all gasoline sold in the U.S. contains some ethanol. The most common blend is E10 (10% ethanol, 90% gasoline).
How Much Ethanol Is in 87 Octane (Regular) Gas?
Standard 87 octane regular gasoline contains up to 10% ethanol — this is the E10 blend mandated across most of the country. The EPA allows up to 10% without a special label, so you may be fueling with anywhere from 0% to 10% ethanol depending on your state and station, though 10% is the norm.
In some Midwest states, E15 (15% ethanol) is sold at select stations and is labeled clearly at the pump. E15 is approved for all 2001 and newer vehicles but not recommended for older cars, motorcycles, small engines, or boats.
How Much Ethanol Is in 93 Octane (Premium) Gas?
Here is the part that surprises most drivers: 93 octane premium gas typically contains the same 10% ethanol as regular gas at most stations. The higher octane rating does not mean less ethanol. Premium fuel reaches its higher anti-knock rating through a different refining process and specific additive packages — not by removing ethanol.
The exception is ethanol-free premium (E0), sold at select marinas, aviation-adjacent fuel stations, and specialty retailers. These fuels are popular with:
- Boats and personal watercraft
- Classic and collector cars
- Motorcycles and ATVs
- Lawn mowers, chainsaws, and other small engines
- Aircraft (avgas)
To find E0 stations near you, visit pure-gas.org.
Ethanol Content Comparison Table: Regular vs. Premium Gas
| Fuel Grade | Octane Rating | Ethanol Content | Blend Name | Common Use |
|---|---|---|---|---|
| Regular | 87 | Up to 10% | E10 | Most passenger cars, trucks, SUVs |
| Mid-Grade | 89 | Up to 10% | E10 | Older vehicles, some trucks |
| Premium | 91–93 | Up to 10% (or 0% E0) | E10 / E0 | High-performance, turbocharged, luxury engines |
| Mid-Grade (E15) | 88 | 15% | E15 | 2001+ vehicles (check owner's manual) |
| Flex Fuel | 100–105 | 51–83% | E85 | Flex-fuel vehicles (FFV) only |
| Ethanol-Free Premium | 90–94 | 0% | E0 | Boats, classics, small engines |
Does Ethanol Content Change Between Regular and Premium at the Same Station?
At the overwhelming majority of U.S. retail gas stations, no — regular and premium are both blended to E10. The station uses the same ethanol base stock; the difference between grades is the octane rating achieved by different hydrocarbon compositions and additive packages, not by varying the ethanol percentage.
Some branded premium fuels (like Shell V-Power NiTRO+ or Chevron Supreme) may advertise a proprietary additive package that can clean injectors and reduce deposits, but this still does not mean they contain less ethanol unless the label specifically says "ethanol-free."
How Ethanol Affects Your Engine
Energy Density — Less MPG on E10 vs. E0
Ethanol contains about 33% less energy per gallon than pure gasoline. With E10, the blend contains 3.3% less energy overall, which translates to a real-world fuel economy reduction of 1–3% compared to ethanol-free gasoline. Most drivers never notice the difference.
Moisture Absorption
Ethanol is hygroscopic — it absorbs water from the atmosphere. This is the primary reason E10 and E15 fuels are not recommended for storage longer than 30–60 days in equipment like lawn mowers, generators, and boats. Water contamination can cause phase separation, where the ethanol and water separate from the gasoline and settle at the bottom of the tank.
Rubber and Plastic Components
High concentrations of ethanol (like E85) can degrade older rubber fuel lines, gaskets, and seals not designed for flex-fuel compatibility. E10 is generally compatible with all vehicles made after 1980 and is safe for modern fuel system materials.
Corrosion Risk in Carbureted Engines
Older, carbureted vehicles and small engines are more susceptible to ethanol-related corrosion, especially in aluminum and zinc components. If you own a classic car or vintage lawn equipment, consider using ethanol-free fuel (E0) when possible.
Does Ethanol in Gas Affect Your Oil?
Yes — and this is something many drivers overlook. Here is how ethanol can indirectly affect your engine oil:
- Moisture introduction: Ethanol can carry water vapor into the combustion chamber. If the engine does not reach full operating temperature on short trips, trace amounts of water can accumulate in the crankcase and dilute or contaminate the oil.
- Acid formation: Combustion byproducts from ethanol can slightly increase the acid content of engine oil over time, accelerating oil degradation.
- E85 and oil dilution: Vehicles running E85 (especially direct-injection engines) can experience fuel dilution of the oil because ethanol has a higher boiling point and may not fully vaporize during combustion.
For most drivers using E10 regular or premium gasoline, this effect is minimal and within the margins that modern engine oil formulations are designed to handle. However, if you use E85 or live in a cold climate with frequent short trips, shorter oil change intervals or more frequent oil inspections are a smart precaution.
A professional mobile oil change is the easiest way to stay on top of your oil health — no shop visit required.
Should You Use Regular (87) or Premium (93) Gas?
The answer depends entirely on your vehicle, not on ethanol content:
| Situation | Recommended Fuel | Reason |
|---|---|---|
| Standard engine (compression ratio < 10:1) | 87 Regular | Designed for regular; premium provides no benefit |
| Turbocharged or supercharged engine | 91–93 Premium | Higher compression needs higher octane to prevent knock |
| High-performance / luxury vehicle (BMW, Audi, Mercedes, Porsche) | 91–93 Premium (required) | Manufacturer requires premium; using regular can cause damage |
| Marine / boat engines | E0 Premium (ethanol-free) | Ethanol absorbs moisture and causes phase separation in marine fuel systems |
| Small engines (mowers, trimmers, generators) | E0 or E10 (check manual) | Many small engines are not designed for E15 or higher |
Bottom line: Always use the fuel grade your owner's manual specifies. Spending more on premium for a car designed for regular provides no performance or efficiency benefit.
Ethanol Content by State — Does It Vary?
The EPA sets the national maximum at 10% for unlabeled gasoline (E10). However, ethanol content can vary by:
- Season: Refiners sometimes adjust blends seasonally for vapor pressure compliance (RVP), which can slightly affect ethanol ratios.
- State mandates: Some states have minimum ethanol requirements. For example, several corn-belt states have minimum blend mandates that effectively guarantee E10 year round.
- Local supply chains: In some regions, you may occasionally get fuel with slightly less ethanol if refiners are adjusting blends for transport or storage reasons.
Regardless of these variations, you can safely assume any unlabeled pump gas in the U.S. contains between 5% and 10% ethanol, with 10% being by far the most common.
Key Takeaways
- 87 octane regular gas = up to 10% ethanol (E10) — the standard across the U.S.
- 93 octane premium gas = up to 10% ethanol (E10) at most stations — same as regular; the octane boost comes from refining, not less ethanol
- Ethanol-free (E0) premium exists at select specialty stations — great for boats, classics, and small engines
- Ethanol content does not differ between grades at standard retail pumps; choose your grade based on your engine's compression ratio and manufacturer specifications
- For most modern vehicles on E10, the impact on oil is minimal — but staying current on oil change intervals is always the best practice
Frequently Asked Questions
How much ethanol is in 87 octane regular gasoline?
Standard 87 octane regular gasoline in the United States contains up to 10% ethanol (E10). This blend is the most common fuel sold at gas stations nationwide and is approved for use in virtually all gasoline-powered vehicles made after 1980.
How much ethanol is in 93 octane premium gasoline?
Most 93 octane premium gasoline also contains up to 10% ethanol (E10), the same as regular. The higher octane rating comes from additives and refining processes, not from a difference in ethanol percentage. However, some premium fuels are sold as ethanol-free (E0), especially at marinas and specialty stations.
Does premium gas have less ethanol than regular?
Not necessarily. Both 87 octane regular and 93 octane premium typically contain the same 10% ethanol (E10) blend at most gas stations. Premium gas achieves its higher octane rating through additives and the refining process — not by reducing ethanol content.
Is there ethanol-free premium gas available?
Yes. Ethanol-free (E0) premium gasoline is available at select stations, particularly those catering to boats, motorcycles, classic cars, and small engines. You can find E0 stations near you using pure-gas.org.
Does ethanol in gas affect oil change intervals?
Yes, ethanol can slightly accelerate oil degradation because it attracts moisture that can mix with engine oil, and combustion byproducts from ethanol can increase acid levels in the oil. Vehicles running E85 or frequently using higher-ethanol blends may benefit from slightly shorter oil change intervals. Always follow your manufacturer's recommendations.
What is the difference between E10, E15, and E85?
E10 contains 10% ethanol and 90% gasoline — the standard blend at most U.S. pumps. E15 contains 15% ethanol and is approved for 2001 and newer vehicles. E85 (flex fuel) contains 51–83% ethanol and is only for flex-fuel vehicles (FFVs).
Keep Your Engine Protected — Schedule a Mobile Oil Change
Whether you use regular 87 or premium 93 octane fuel, staying on top of your oil change schedule is the single most important thing you can do for your engine. Skip the shop — let our certified technicians come to you.