​​Do I Have to Put Premium in My Car? What Happens if I Don’t?​

Some cars, especially those with high-performance engines, recommend using premium fuel. Is it necessary?  And what occurs if you don’t? Alderman Automotive has the answers. 

Nearly every gas station gives you a choice between regular and premium fuel, and true to its name, premium fuel costs more. Is it better for your car, and should you use it?  The short answer is: “Maybe not.” But let’s explain a bit. 

First of all, let’s clarify what premium fuel is not. It does not possess a higher energy density, nor is it cleaner or the product of a higher refining quality. What sets premium fuel apart from regular fuel is its higher-octane rating. Octane is a measurement of how well the fuel resists knocking or pinging in the combustion chamber.  

The 4-Cycle Process in Brief 

To explain knocking, we must quickly review the 4-cycle combustion system of your gas engine: 

1. The intake valves open, the piston goes down, drawing in the air-fuel mixture. 
2. With the valves closed, the piston moves up, compressing the air-fuel mixture.  The difference in volume between the piston’s position at the bottom and at the top is known as the compression ratio (which will become important shortly). 
3. Valves are closed, the spark plug ignites the air-fuel mixture, and the combustion causes expansion, which pushes the piston down. This is the power stroke. 
4. Exhaust valves open, and the piston moves up, pushing the burnt air-fuel out.

A Burn Versus Explosion 

A misconception is that the spark explodes the air-fuel mixture, but it is actually a rapid yet controlled burn that creates an expansion, pushing the piston down. The difference between this and an explosion is akin to the difference between using all your strength to push a refrigerator across the floor or employing the same effort to strike it with a sledgehammer. Pushing moves it across the floor, while the sledgehammer moves it slightly—but mostly damages the refrigerator.  

Generally, the higher the compression, the more power is generated; however, if the compression is too high for the fuel’s octane level, it leads to detonation. This significantly reduces power, and your pistons begin to suffer damage. The terms “knocking“ and “pinging” originate from the sound produced by these minor explosions, resembling someone tapping the cylinder heads with a tiny hammer.  

Most Engines Run Fine on Regular 

Most engines today have compression ratios set to accommodate regular gasoline.  Turbocharged engines feature even lower ratios because forcing more air-fuel into the cylinder effectively increases compression. Therefore, if your engine recommends premium fuel, it is likely turbocharged. 

However, that doesn’t mean your turbocharged engine requires premium fuel. This is because modern engines are equipped with knock sensors. These act as small microphones that detect knocking and if it occurs, signal the engine to delay the ignition timing, effectively lowering the compression until the knocking ceases. This results in a slight power reduction, which is the crux of the issue. If you possess a high-performance turbocharged engine, it must operate on premium fuel to achieve its specified horsepower and torque ratings. 

The Bottom Line 

If you use regular fuel in your car and don’t hear knocking (which is most likely), then using premium fuel could be a waste of money. If you have a high-performance engine that doesn’t knock with regular fuel, and you are satisfied with the power output, then again, premium fuel may be unnecessary. However, if you want to extract every bit of power from that high-performance engine, or if you own a high-performance vintage car from the leaded-gas era, you will probably want to use premium fuel. 

Thus, we come back to “probably not.” However, it’s always best to use whatever fuel the manufacturer recommends. If the manufacturer requires premium, then use premium. Visit us at Alderman Automotive to see our robust inventory. We’re always here to help you with any questions you may have.