What happens if you accidentally put regular gas instead of premium in an Acura?
Using regular gasoline in an Acura that requires premium can trigger the car’s knock-detection system to retard ignition timing, which may reduce power and efficiency. Refuel with premium at the next fill and drive normally unless you notice abnormal symptoms.
Details vary by model and octane gap. Turbocharged or high-compression engines are more sensitive to octane, and many Acura models specify premium. A one-time misfuel is unlikely to cause immediate harm, but repeated use of regular can increase wear over time. Always check your owner's manual for the exact octane requirement for your model.
Why octane matters for Acura engines
Octane rating measures a fuel's resistance to pre-detonation. In high-compression or turbocharged engines, using the recommended premium fuel helps maintain optimal timing and performance; regular gasoline can cause knocking, especially under heavy load or high boost.
- Octane resists premature detonation (knock) under compression and boosting.
- Premium gasoline typically has 91 octane or higher, as used by many Acura engines with higher compression or forced induction.
- Modern engines use knock sensors and timing adjustment to protect themselves, which can reduce power if the engine detects low-octane detonation.
- Using regular fuel regularly can lead to reduced performance and, over time, more wear on components sensitive to timing and heat.
For model-specific guidance, consult the owner's manual or the fuel-filler sticker in your vehicle since some base models can tolerate regular while others require premium.
What you might notice if you accidentally use regular
Even a single misfuel can produce noticeable symptoms in some Acuras, particularly those with turbochargers or high-compression engines. Here are common signs drivers report.
- Engine knocking or pinging under acceleration or when climbing hills
- Reduced power and slower throttle response
- Lower-than-expected fuel efficiency
- Occasional rough idle or misfires in some conditions
- Check Engine Light or a warning related to detonation if the issue persists
Keep in mind that symptoms can be subtle and may only appear under load; if you hear persistent knocking, stop driving and refuel with the correct octane as soon as possible.
What to do if you filled with regular by mistake
The right course is to switch back to the recommended fuel at the next fill and avoid aggressive driving until you’re back on the correct octane. If you notice persistent knocking or warning lights, have the vehicle inspected by a dealer or a qualified technician.
- Refuel with the recommended premium octane at the next opportunity, and ensure the fuel door label matches the engine's requirement (91 octane or higher for many turbo/high-compression Acura engines).
- Drive conservatively for the next few hundred miles, avoiding hard accelerations and lugging the engine.
- If knocking or performance issues continue after refueling, schedule service to check for potential damage and confirm the engine control system is adapting correctly.
- Do not ignore warning lights; if the check engine light or a knock warning persists, seek professional inspection promptly.
Note: The risk is higher on turbocharged or performance-oriented models, where octane sensitivity is greater. For other Acura models, regular gasoline may be acceptable if it meets the manual’s minimum octane requirement, but premium is still recommended to preserve performance and efficiency when specified.
Model-specific notes
Acura’s fuel recommendations vary by engine and trim. The most important guidance is to follow the exact octane specified for your model in the owner's manual or on the fuel-filler door sticker.
- Turbocharged engines (for example, certain TLX, RDX, and MDX configurations) typically require premium (91 octane or higher) for optimal performance and longevity.
- Naturally aspirated, non-turbo engines in older models may tolerate regular, but Acura generally recommends premium for peak performance.
- Hybrid variants may have separate fuel recommendations; always verify for your specific model year.
Bottom line: A one-off misfuel is unlikely to cause immediate disaster, but regular use of regular fuel in premium-requiring engines can cause knock, reduced power, and potential long-term wear. When in doubt, rely on the owner’s manual or consult your local Acura dealer for model-specific guidance.
Summary
If you accidentally fill up with regular instead of premium in an Acura that requires premium, expect possible engine knock and performance loss as the ECU retards timing to protect the engine. Refill with the correct octane as soon as possible and drive gently until you’re back on the recommended fuel. Always follow the octane specification in the owner’s manual for your exact model and seek service if symptoms persist or warning lights appear.
