Most gas-powered vehicles run on regular fuel; however, some require premium. Besides the heftier price tag, the main difference between regular and premium gas is the octane rating or grade. Regular gas generally has a grade of 87, while premium gas ranges between 91 and 94.
The higher the octane level, the more resistant the fuel is to early detonation. Mixing gas grades alters the octane rating of the fuel in the tank. In fact, most gas stations offer an 89-octane “midgrade” option that is a blend of regular and premium gas.
If your car is built for regular gas, adding in some higher-octane fuel shouldn’t cause any harm to it.
However, premium vehicles that require a higher octane level of gasoline might see a minor performance decrease or engine knocking.
Here’s what you should know about mixing regular and premium gas:
How Does Premium Differ From Regular Gas?
Premium gas has a higher-octane rating than regular gas. It ranges from 91 to 94, depending on where you live. On the other hand, regular gas has an octane level of 87.
Gasoline with higher octane rating is ideal for preventing engine knock, which might explain why people sometimes use premium gas in regular gas vehicles.
What Happens If You Mix Premium and Regular Gas?
From a numerical view, if you mix equal parts of regular gas with premium gas (mix 87 and 91 gas), you’d end up with an effectively combined grade of 89. However, this will depend on what quantity of each you have added.
It’s best to remember that lower octane for your premium car might result in reduced performance; therefore, fill yours with premium gas. However, if there are no premium pumps and you fear risking your car knocking, don’t worry. Instead, fill it with just enough gas to reach the nearest gas station.
On the other hand, if your car requires regular fuel, it’s best to fill it up with regular fuel because premium gas doesn’t have any added benefits in most cars. However, if you own a car with turbochargers or a heavy engine, you will need high-octane gas because these vehicles come with higher compression ratios. Therefore, failure to use premium gas might result in knocking.
If you own an older car, it’s advisable to use premium gas instead of regular.
What Will Happen if You Mix Regular and Premium Gas in a Premium Gas Car?
A few years ago, mixing premium and regular gas could mess up your car and result in an engine knock. This meant that your car would start knocking immediately after refueling before departing from the gas station.
However, today things have changed and are different. For example, if you accidentally put regular gas in your premium vehicle, such as BMW, your car’s Engine Control Unit (ECU) will automatically adjust its engine performance and timing.
While your car can work with lower-octane fuel, it’s not advisable to do so repeatedly because it’s cheaper; manufacturers built the car to use higher-octane fuel; therefore, the safest option is to stick with this option much as possible.
How Do You Know If Your Car Requires Regular or Premium Fuel?
You can find the required fuel grade on a label inside the gas door. However, with time, this label might fade or fall off.
The best thing is that the owner’s manual will also detail the octane rating your engine is designed for. Alternatively, you can also provide your car’s VIN to the correct dealer to determine the correct gas grade.
So, Can You Mix Regular and Premium Gas?
You can do several things to extend your vehicle’s life; however, filling your gas tank with the wrong fuel grade isn’t one of the things.
If you accidentally add premium fuel to your car that requires regular fuel, nothing bad will happen to the engine. However, you won’t get any benefits; therefore, don’t expect more power or improved fuel economy.
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On the other hand, accidentally adding regular gas to a car that requires premium gas isn’t a crisis either, as long as this doesn’t happen often. If you notice the engine knocking after adding regular fuel, you might be able to resolve the issue by pouring an octane booster into the tank.
Remember that you can extend your vehicle’s longevity by using the correct fuel grade and only filling up at top-tier gas stations.