When you stand at the gas pump, staring at the array of fuel choices, one question often comes to mind: What grade of fuel should you use for your car? Is it okay to settle for the standard 87-octane, the most affordable option? Does the octane rating even make a difference? Here’s the lowdown on selecting the right fuel for your vehicle.

It’s Not About the Highest Octane, It’s About the Right Octane

When it comes to fueling your car, the crucial factor isn’t choosing the highest octane available, but rather the octane your vehicle requires. Consult your car’s owner’s manual to find out the specific octane rating it recommends. If your manual states that 87-octane is sufficient, there’s no need to splurge on premium gas. Higher octane fuel won’t enhance your car’s performance in such cases.

However, if your owner’s manual mandates a minimum octane of 91 to 93, it’s imperative not to skimp on quality. Using lower-octane fuel can lead to issues down the road, potentially costing you more. The rule of thumb is to adhere to your manual’s recommendations regarding the acceptable octane rating.

Why Do Some Cars Require Higher Octane?

Before diving into the specifics, it’s essential to grasp the concept of octane. When you ignite the engine, a spark initiates the combustion of the air and fuel mixture in your car’s engine, powering your vehicle. Sometimes, this mixture can ignite prematurely, causing a knocking sound known as preignition. Modern cars are equipped with knock sensors to prevent this issue.

The octane rating of your gasoline has no bearing on its energy content. Instead, it signifies how easily the air-fuel mixture ignites. Higher octane indicates greater resistance to preignition, requiring more agitation to ignite. This resistance to premature ignition is what the octane level is all about.

In some high-performance cars, a higher fuel-air compression ratio generates more power, but it also increases heat and the likelihood of early ignition. Higher octane gasoline mitigates this problem effectively.

The Consequences of Using the Wrong Gas

Your car’s gas cap or the instructions near it usually specify the fuel type your vehicle requires. You can also consult your owner’s manual for precise fuel recommendations.

If your car requires premium gas and you opt for a lower octane like 87, you can anticipate knocking, preignition, and potential engine damage. Modern vehicles incorporate knock sensors, which can mitigate preignition, but this may reduce engine power and fuel economy, essentially costing you more in the long run. It’s also conceivable that your knock sensor may malfunction or react slowly, potentially resulting in engine damage over time.

Should I Always Use Premium Gas When Indicated?

Some cars may suggest “premium fuel recommended.” In such cases, your car is safe to run on regular 87-octane gas, but there may be advantages to using higher-octane fuel. You can choose to stick with the more affordable option or experiment to gauge whether the fuel economy and power differences justify the higher cost of premium fuel.

However, using higher octane fuel in a vehicle not designed for it is generally a waste of money. If your car isn’t designed for premium fuel, there’s no significant benefit to using it.

Diesel Engines: A Different Ball Game

If your vehicle runs on diesel fuel, you’re dealing with an entirely distinct system. There’s no room for negotiation when it comes to fuel. Diesel engines require diesel fuel exclusively. Introducing regular or premium unleaded gasoline into a diesel engine can lead to catastrophic damage and render the vehicle inoperable.

Considerations at High Altitudes

In high-altitude locations, you might encounter gas stations offering lower-octane gasoline than you’re accustomed to. In the past, older cars could cope with lower octane levels in thin air, but modern fuel-injection engines differ. It’s advisable to use at least 87-octane gas or higher, even if you typically use 87, 88, or 91-octane gas. Luxury car owners should plan ahead when traveling to high-altitude areas, ensuring they have access to the required octane level.

International Variations

For foreign cars designed for sale in the U.S., standard octane ratings apply. However, cars purchased or intended for purchase outside the U.S. may specify a Research Octane Number (RON) rather than the U.S. octane rating. These numbers don’t align perfectly. For instance, if your European car calls for RON 95, you should use regular or 87-octane gas. If it asks for RON 98, opt for premium 93-octane fuel.