Why 93 Octane Can Be Better Than 87—And When It Isn’t

93-octane gasoline resists engine knock better than 87, allowing higher-performance or turbocharged engines to run more spark advance and boost for more power and, in some cases, slightly better efficiency. But if your engine is designed for 87, moving to 93 usually won’t add power, increase mileage, or clean your engine—it will mostly just cost more.

What Octane Really Measures

Octane is a fuel’s resistance to knock—the uncontrolled, spontaneous combustion of the end-gas in the cylinder that creates sharp pressure spikes and a metallic “ping.” In the United States, pump labels show Anti-Knock Index (AKI), the average of Research Octane Number (RON) and Motor Octane Number (MON). A higher octane rating (e.g., 93 AKI) means the fuel can tolerate more heat and pressure before auto-ignition, letting engines with high compression ratios, aggressive ignition timing, or turbo/supercharging operate at their intended performance without knock-induced timing pull.

When 93 Octane Delivers Real Benefits

Some engines are engineered to take advantage of higher octane. In these cases, 93 allows the powertrain to run closer to its optimal calibration, improving acceleration and, sometimes, efficiency under load.

• Premium-required engines: Many high-compression or boosted engines specify 91/93 AKI as “required.” Using 87 can trigger knock control, reduce power, and risk long-term stress; 93 lets them meet their rated performance.
• Premium-recommended engines: Numerous modern turbocharged/direct-injection engines (e.g., many BMW, Mercedes, VW/Audi, Ford EcoBoost trims) run on 87 but deliver their advertised horsepower on 91/93. Gains of roughly 3–10% in peak power are common; efficiency improvements are typically smaller (around 1–3%) and most evident under heavy load.
• High-load, high-heat conditions: Towing, mountain grades, or hot climates increase cylinder temperatures. Higher octane helps maintain timing and avoid knock when the engine is working hard.
• Track or spirited driving: Repeated high-load operation benefits from the added knock margin of 93, stabilizing performance lap after lap.
• Engines sensitive to carbon buildup: If mild knock occurs due to deposits raising compression, 93 may reduce audible pinging—though the proper fix is cleaning or repair.

In short, if the vehicle’s design or your driving conditions push cylinder pressures high, 93 octane offers tangible, measurable advantages and preserves the calibration the engineers intended.

When 93 Won’t Help (and May Cost More)

For many daily drivers tuned for regular fuel, higher octane doesn’t unlock extra energy or cleanliness—it simply offers knock resistance the engine doesn’t need.

• Engines designed for 87 AKI: If your owner’s manual says 87 is fine and you don’t hear knock, 93 typically won’t increase power or mileage.
• Light-duty commuting: Low-load, steady-state driving rarely approaches knock limits, so the ECU won’t exploit the extra octane.
• Fuel economy myths: Octane isn’t energy content. Premium often has the same or slightly lower energy per gallon (especially if ethanol content differs), so MPG usually doesn’t improve and can even dip slightly.
• “Cleaner fuel” misconceptions: Detergent levels depend on brand and whether the station is Top Tier certified—not on octane grade. 93 isn’t inherently cleaner.
• Cost premium: In the U.S., premium commonly costs 40–70 cents more per gallon (and sometimes more), a price hike unlikely to be offset by MPG gains in 87-tuned engines.

If your vehicle runs smoothly on 87 without pinging, stepping up to 93 is generally an unnecessary expense.

Common Misconceptions

Octane has been conflated with power, cleanliness, and longevity. Here’s what it does—and doesn’t—do.

• Octane vs. power: Higher octane doesn’t contain more energy. It allows certain engines to use more timing/boost, which produces more power—if the engine is calibrated for it.
• Octane vs. detergents: Cleaner injectors and valves come from detergent packages. Look for Top Tier gasoline, which standardizes robust detergents across all grades.
• Ethanol and octane: Ethanol raises octane but has lower energy density than pure gasoline. E10 (10% ethanol) is common in both 87 and 93; regional blends vary.
• Knock vs. pre-ignition: Knock is end-gas auto-ignition after the spark. Pre-ignition occurs before the spark and can be severe (e.g., LSPI in some small turbo DI engines). Using the recommended octane helps manage knock; LSPI also depends on engine design, oil formulation, and operating conditions.
• Warranty and labeling: “Premium required” means use it. “Premium recommended” means you may use 87, but power/response can drop. Following the manual protects performance and warranty coverage.

Understanding these distinctions helps you choose fuel for performance or value without chasing myths.

How to Know What Your Car Needs

Matching fuel to your vehicle and usage is straightforward with a few checks and simple tests.

• Read the owner’s manual and fuel door: Look for “required” vs. “recommended.”
• Listen for pinging under load: If you hear knock on 87 during climbs or hot days, 91/93 may help—if the manual allows it.
• Use onboard data: Some performance-minded drivers monitor knock retard via OBD-II to see whether higher octane reduces timing pull.
• Consider your use case: Heavy towing, desert heat, or track days favor higher octane; gentle commuting does not.
• A/B test carefully: Run two to three tanks of 87 vs. 91/93, controlling for route, temperature, and tire pressure, and calculate hand-logged MPG and observe drivability.
• Mixing fuels: It’s generally safe to mix. Octane blends roughly linearly (half a tank of 93 with half of 87 yields about 90 AKI).

These steps let you align fuel choice with your vehicle’s engineering and your real-world demands.

Price and Regional Differences

What’s “premium” depends on where you live—and how octane is measured.

U.S. vs. International Labels

U.S. pumps display AKI. Many other countries post RON. Roughly, 93 AKI is similar to 98 RON, and 87 AKI aligns with about 91–92 RON. Also, some U.S. regions only offer 91 as the highest grade; others carry 93 or even 94.

Seasonal and Ethanol Impacts

Most retail gasoline is E10 year-round, but blends vary by region and season. Ethanol boosts octane but lowers energy density slightly, which can nudge MPG. Some stations sell ethanol-free premium (often for marine/small engines), which may have higher energy content despite the same or lower octane. Detergent quality depends on brand and Top Tier status, not octane.

Bottom Line

93 octane is “better” only if your engine can use its higher knock resistance—typically in premium-required or premium-recommended, high-compression, or boosted engines, or under heavy load and heat. For vehicles designed for 87 and used gently, 93 brings little to no benefit beyond a lighter wallet.

Summary

93 octane resists knock more than 87, enabling greater timing and boost in engines built for it, which can increase power and preserve performance in hot or high-load conditions. If your car is tuned for regular fuel and you drive moderately, 93 won’t add power or MPG and isn’t cleaner by default—choose the octane your owner’s manual specifies, and pick a Top Tier brand for deposit control.