Do you need Premium – Yes
Regular gas is just as good as premium when it comes to your average car. High-performance engines are the ones that need high-octane fuels. The octane rating determines how easy the gasoline is to ignite, and a higher octane means that the fuel is less volatile. It needs to be less volatile because performance engines often have high compression, and the more fuel is compressed, the easier it is to ignite.
When low-octane fuel is used in a performance engine, the compression is enough to ignite the fuel before the engine sparks. This leads to a premature explosion in the cylinder, which can create massive stresses on the piston and rod, sometimes causing them to bend or break (leaving you needing an expensive repair, or a new engine). You can hear the early warnings sign in an engine "knock" which is easiest to hear under acceleration or up a gradual hill.
Your average engine has a low compression ratio, and would gain no performance or benefit out of premium fuel. Regardless, you should first check with your owner's manual, or car dealer if you are unsure. Some gas stations such as Shell also promote their premium gas as having special cleaning properties. This could be true, but you don't need to spend extra for Shell V-power when you can get the same benefits from your local auto supplier. Fuel additives like STP fuel injector cleaner are cheaper alternatives, which perform the similar cleaning roles without the price. And if your fuel system is blocked, the only way to properly clean it out is to have it flushed by a mechanic.
Even high-compression motors don't necessarily need premium gas. Most automotive stores carry octane boosters that can be used with regular gasoline to fulfill the role of premium. In these cases, you should check with your car dealer before trying it out, as some products can void the warranty for your power train. If your car is past its warranty period, or your dealer says it isn't a problem, then you might be able to save some money. They even offer a lead alternative for classic cars, but that's another story.
Also, new computer technologies have helped to eliminate problems like engine knock. These systems use sensors placed throughout your engine and relay to a central computer that makes decisions about engine timing and fuel. This means some new cars can utilize the benefits of high-octane fuel and live happily on regular gas just the same. Once again, you should check your owner's manual to see what minimum octane rating your car needs to run at its peak.
