Premium Vehicles Require Premium Gas
At Aardvark Automotive, we work on a lot of luxury vehicles, like Mercedes, BMW, and Audi—cars that ask for premium, top-tier gasoline. Sometimes our customers innocently inquire, “Would it be ok to fill up with regular?” despite what their manuals say. The answer is “no,” but we understand it’s helpful to know why. With this blog, we’ll explain what your vehicle’s octane rating means and the reasons it’s important.
First of all, let us reassure you that requiring the use of premium gasoline is not a shady deal between automakers and gas companies to make you pay more at the pump. Engines that require top-tier gas are often built for performance, and using regular gas is a good way to end up with a dead engine and a hefty repair bill.
What’s octane, and why does it matter?
Octane is the number associated with different grades of gasoline, for example, 87 for regular and 93 for premium. The number measures how easily the gas will spontaneously combust under pressure. This doesn’t mean gasoline can simply explode on its own. What it does mean is that when your car’s engine pulls gasoline into a cylinder, it uses the pistons to squish a mixture of gasoline and air before using the sparkplugs to explode it.
The amount of gasoline + air mixture that’s squished is your engine’s compression ratio. The more gas and air you can squeeze, the more powerful the explosion—and the more powerful the engine.
Can using regular gas hurt my car if it asks for premium?
Think back to high school chemistry class… Maybe you remember that things heat up when you compress them. If you squish gasoline too much, it will explode before the sparkplug gets a chance to light it. Premature explosion is bad because it won’t burn up all the gas/air mixture, and can leave scorched deposits in your cylinders. It can also damage some of the delicate moving parts inside your engine.
Using regular fuel in a vehicle that requires premium—or higher octane fuel—will lead to premature combustion as the pistons compress the regular gas past the level at which it combusts.
So if your manual asks for premium gasoline, don’t try to save money by paying a few cents less for regular gas. The investment is more than worth it in terms of your car’s performance and how long the engine will last. Even cars that only “recommend” premium gas should be fed premium. Using regular could reduce the performance and efficiency of your engine, causing you to get fewer miles per gallon, and cancelling any money you saved by buying cheaper gas.