Most pre-2025 Audi models can technically run on regular 87-octane gas without immediate engine damage, but performance, fuel economy, and long-term reliability will suffer[1]. However, all 2025 Audi models now require premium 91-octane fuel—this is not a recommendation but a requirement printed on the fuel door and owner's manual[2]. Using regular gas in performance S and RS models at any model year risks significant engine damage and warranty denial[1].

Why Audi Engines Need Higher Octane Fuel

Audi vehicles use turbocharged, high-compression engines that generate more power from smaller displacements[1]. This engineering approach requires fuel that can withstand higher pressures before igniting.

Octane rating measures fuel's resistance to premature combustion, known as knock or ping[1]. When fuel ignites before the spark plug fires, it creates pressure waves that hammer against engine components. Occasional knock is unlikely to cause damage, but repeated knocking can destroy pistons, valves, and cylinder walls over time[3].

Premium gasoline (91–93 octane in the US) resists knock better than regular fuel (87 octane)[1]. This stability allows Audi's ECU to run more aggressive ignition timing and higher boost pressures, delivering the power and efficiency the car was engineered to provide.

Modern Audis have knock sensors that detect lower-octane fuel and automatically retard timing to prevent damage[1]. This safeguard protects the engine but results in noticeably reduced power and worse fuel economy.

Fuel Requirements by Model Year

Audi's fuel recommendations have evolved significantly. Understanding whether your specific Audi recommends or requires premium is critical.

Pre-2025 Models (Premium Recommended)

Many Audi models before 2025 carried labels stating premium is recommended but 87 octane is acceptable[1]. Common language in owner's manuals read:

• "For best performance and fuel economy, use premium unleaded gasoline with a minimum octane rating of 91"
• "If premium is not available, regular unleaded gasoline with an octane rating of 87 can be used. However, performance may be reduced"

This applied to models including:

• A3, A4, A5 (base trims)
• Q3, Q5 (standard powertrains)
• Some A6, A7 configurations

2025+ Models (Premium Required)

Starting with the 2025 model year, Audi standardized premium fuel requirements across all vehicles sold in North America[2]. The fuel door, owner's manual, and dealer bulletins explicitly specify 91 octane minimum[2].

This change reflects:

• Turbocharging now standard across the entire lineup
• Stricter emissions standards requiring optimal combustion
• Consumer expectations for consistent performance

S and RS Models (Always Required)

All Audi S and RS performance models—S3, S4, S5, S6, S7, RS3, RS5, RS6, RS7, RS Q8—have always required premium fuel regardless of model year[2]. These high-compression, aggressively tuned engines have zero tolerance for lower-octane fuel.

If you're exploring which Audi has the most horsepower, understand that higher-performance engines are even more dependent on premium fuel.

What Happens If You Use Regular Gas

The consequences of using 87 octane in an Audi depend on the model, driving conditions, and frequency of use[3].

Immediate Effects

• Reduced power: 10–15% loss as the ECU retards ignition timing and reduces turbo boost[4]
• Worse fuel economy: 2–4 MPG decrease as combustion becomes less efficient[4]
• Engine knock under load: Particularly during hard acceleration, climbing hills, or towing[3]
• Sluggish throttle response: Delayed acceleration as the engine compensates for lower octane[1]

Long-Term Consequences

• Carbon buildup: Incomplete combustion leaves deposits on intake valves and fuel injectors[1]
• Component wear: Repeated knock events, even minor ones, accelerate wear on pistons and bearings[3]
• Catalyst damage: Unburned fuel reaching the exhaust can damage catalytic converters[4]
• Warranty complications: Using incorrect fuel voids coverage for related engine damage[2]

Cost Analysis: Regular vs Premium

Many drivers consider regular gas to save money. The math often doesn't support this assumption.

Per-Mile Cost Comparison

The $0.50/gallon premium difference is often offset by improved fuel economy[4]. In many cases, premium actually costs less per mile driven when accounting for efficiency gains.

Hidden Costs of Regular Gas

Beyond fuel efficiency, using regular gas in a premium-recommended Audi can lead to[4]:

• Increased maintenance from carbon buildup
• Potential engine repairs from knock damage
• Lower resale value if fuel-related issues are documented

If you're concerned about overall ownership costs, understanding how many miles an Audi can last helps frame the long-term value of proper fueling.

Model-Specific Fuel Requirements

Always verify your specific vehicle's requirement by checking the fuel door label or owner's manual[2].

Emergency Situations: When Regular Is Acceptable

If you're in an area where premium fuel is unavailable, Audi provides guidance[2]:

1. Use the highest available octane (89 midgrade is better than 87 regular)
2. Avoid hard acceleration and high engine loads
3. Refuel with premium as soon as possible
4. Keep the tank above half full to dilute lower-octane fuel faster

This applies only to models where premium is "recommended" rather than "required." For S, RS, and all 2025+ models, avoid regular fuel entirely if possible[2].

Key Takeaways

• Pre-2025 Audi models with "premium recommended" can run on 87 octane without immediate damage, but performance and economy suffer
• All 2025+ Audi models require 91 octane minimum—this is now mandatory, not a recommendation
• S and RS performance models have always required premium fuel regardless of model year
• Premium gas often costs less per mile than regular when accounting for improved fuel economy
• Using regular gas in a required-premium Audi can void warranty coverage for engine-related damage

Frequently Asked Questions

Will using regular gas once damage my Audi?

Why do some Audi dealerships say regular is fine?

Does premium gas clean my engine?

Can I mix regular and premium gas?

What about 93 octane vs 91?

References

1. Car and Driver. (2020). Do Audis Require Premium Gas? https://www.caranddriver.com/research/a33233972/do-audis-require-premium-gas/
2. VehQ. (2025). Do Audi Cars Need Premium Gas? Model-by-Model Guide. https://vehq.com/do-audi-cars-need-premium-gas/
3. Premier Tire. (2024). Can I Use Regular Gas in My Premium Gas Car? https://www.premiertire.us/can-i-use-regular-gas-in-my-premium-gas-car
4. Audi Jacksonville. (2024). Best fuel for Audi. https://www.audijacksonville.com/the-right-fuel-for-your-audi--ensuring-peak-performance-and-efficiency.htm
5. Reddit r/Audi. (2024). Why do base model Audi's require premium fuel, but higher end VW's don't? https://www.reddit.com/r/Audi/comments/1eq41qx/