While most gas-powered cars run on Regular fuel, some require Premium. Besides the higher price tag, the octane rating, or grade, is the main difference. Regular gas generally has a grade of 87, while Premium ranges between 91 and 94.
The higher the octane rating, the more resistant the fuel is to early detonation.
Can you mix Premium and Regular gas? Combining fuel grades essentially just alters the octane rating of what’s in the tank. In fact, many gas stations offer an 89-octane “Midgrade” option that’s merely a blend of Regular and Premium.
So, is it harmful to mix gas grades?
In cars built for Regular, adding in some higher-octane fuel shouldn’t cause any harm.
However, putting Regular fuel in a Premium car will not only lead to reduced performance but may result in enduring engine damage.
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What Happens If You Put Regular Gas In A Premium Car?
Higher-compression engines, like those with forced induction (i.e., turbocharged), are engineered to extract as much performance out of a motor as possible.
However, they also create additional pressure and warmth, which might result in early ignition of lower-quality fuel, a problem that may result in engine knock.
Engine knock, or “pinging,” essentially means the air/fuel mixture inside the combustion chamber is not igniting evenly. While the sporadic knock is acceptable, persistent knocking can cause lasting damage to crucial engine components, including the pistons, crankshaft bearings, and cylinder walls.
Unsure what engine knock sounds like? This short video from YouTube’s Motorcarnut provides an excellent illustration.
Because of the higher-octane rating of Premium fuel, it is not as prone to early ignition. This allows the Electronic Control Unit (ECU) of the vehicle to have sufficient time to enhance detonation, hence improving performance and effectiveness.
Engine knock can stem from several things, like defective spark plugs or carbon buildup, but low-octane fuel is one of the most common.
What Happens If You Put Premium Gas In A Regular Car?
The benefit of Premium fuel is that it allows the ECU time to optimize detonation. However, a car designed for Regular fuel doesn’t generate sufficient pressure or heat for early ignition to be an issue.
While filling up with Premium might sound like a way to coddle your car, there’s really no advantage if it’s made for a lower-octane rating.
Can you mix 87 and 91 gas? Sure, but you’re essentially just tossing away money. Instead, save yourself the 50 cents per gallon and opt for the gas grade your car is designed for.
How Do You Know If Your Car Takes Regular Or Premium Fuel?
You’ll find the necessary fuel grade on a label inside the gas door. With time, though, this label may fade or fall off. Thankfully, the owner’s manual will also detail the octane rating your engine is designed for.
Finally, you can also provide your car’s VIN to a nearby dealer to find out the appropriate gas grade.
So, Can You Mix Different Grades Of Gas?
There are a lot of things you can do to extend the life of your vehicle. However, filling the gas tank with the wrong fuel grade is not one of them.
If you accidentally add Premium fuel to a car built for Regular, nothing detrimental will occur to the engine, and you can drive without worry. However, you also won’t get any advantages, so don’t expect improved fuel economy or more power.
Mistakenly adding Standard to a car designed for Premium isn’t a catastrophe either, so long as it doesn’t happen often.
If you do notice the engine knocking after adding Regular fuel, you may be able to resolve the issue by pouring an octane booster into the tank.
In addition to using the proper fuel grade, filling up exclusively at Top-Tier gas stations can help extend your vehicle’s lifespan.
