The type of gas your vehicle needs is dependent on the type of vehicle you have
Does the type of gas you put in your car really matter?
The answer is that it depends.
When it comes to regular vs. premium gas, the short answer is that if your vehicle manual says it requires premium gas, then you need to fill it with premium gas. If it doesn’t, then using premium gas is generally unnecessary.
Why Do Some Vehicles Require Premium Gas?
The primary vehicle type using premium gas is the luxury class, but some SUVs have been known to use it too. The reason these vehicles require premium gas is due to the high compression ratio of their engines. High compression ratio means that the total volume displaced inside the cylinder by piston movement is higher than the average vehicle.
When you use regular gas in a vehicle that requires premium high-octane gas, it may cause premature ignition inside the chamber, which will result in knocking and rattling sounds. An accidental use or two of regular gas might not cause any problems, but regular use will likely cause damage eventually.
On the other hand, premium gas won’t harm your low compression vehicle, but it won’t have any real benefit either. In other words, it’s not worth the extra price if your vehicle doesn’t actually require it.
Octane Ratings Explained
When you fill up, you might notice that the pump usually has three numbers indicating the octane rating of each gas type. Regular is usually 87, mid-grade is 89 and premium is 91 or sometimes 93.
What do these numbers mean?
The meaning is related to pre-ignition. Air and fuel are ignited with a spark to run your engine. Early ignition of this mixture is what causes the knocking sound. Cars in the present day have sensors to prevent pre-ignition, so you won’t hear it much under normal circumstances.
Octane ratings refer to the gasoline’s ability to resist early ignition. High octane means higher resistance. Octane ratings don’t have anything to do with giving the fuel more energy. This myth is what has convinced some drivers to use premium gas in their regular fuel cars, which is largely a waste of money.
Regular or Premium?
If your car is like most vehicles, and there’s no indication in the owner’s manual to the contrary, 87-octane fuel is what you should use. If your car manual indicates that premium gas is not just recommended, but required, then you should always use the 91 or 93-octane gas.
In earlier cars, using lower octane gas would ensure engine damage. However, modern cars can actually retune the engine to avoid early ignition with lower octane gas.
That doesn’t mean you should use it though.
The lower octane gas will reduce your power and fuel efficiency, and it can still cause damage in the long run if you keep using it.
Some cars might say that premium fuel is recommended in your engine. In that case, you can run any fuel grade between regular and premium in your car without damaging your engine. Sometimes cars with this indication get better gas mileage and put out more power with higher grades of fuel.
You can try each grade in your tank and see if there is a difference in your vehicle’s performance before committing to one or the other.
If you buy a European car, you might see RON 95 or RON 98 as the gas indicated for your vehicle. These are octane grades calculated in a different manner than the United States. RON 95 is much the same as 87-octane and RON 98 is equal to 94-octane, but 93 typically suffices.
High Altitude Octane
When in high altitude locations, you might see gas rated at 85-octane. The idea behind lower octane fuel in high altitudes is that the thin air lowers compression in the engine.
However, this doesn’t hold true for modern fuel-injected vehicles. The best practice here is to look at the numbers. Buy 87 if your car takes regular, even if it’s midgrade price.
The bottom line is to always check your owner’s manual for recommended fuel grade and stick to it.