There is no doubt about it; premium gas can put a dent in your wallet. In general, gas stations price premium substantially higher than regular, and topping your tank with it can be expensive. With unpredictable swings in gas prices, it can sometimes just seem more practical to gas up with regular. Some vehicle manufacturers extend the recommendation of premium gas in certain makes and/or models. As you can imagine, the question arises: Is it really necessary or is it just a ploy to further line the pockets of oil companies?
So, is premium gasoline really necessary? And if you don't use premium, could it void your warranty or, worse yet, cause damage to your engine? You might be surprised by the answers.
The Difference Between Requirement and Recommendation
A manufacturer's requirement for premium fuel is really because the components of the vehicle's fuel system is engineered to perform to its highest potential with a higher-octane fuel. If you fill up such a vehicle with regular fuel, you may indeed be voiding a warranty. This will most often come into play if substituting regular for premium leads to significant engine knock or pinging that causes damage to the pistons or other engine components. Aside from those complications, you could also experience a decrease in fuel efficiency and overall engine performance.
That said, manufacturers may simply recommend premium gas for best performance in certain makes and models, but also include that you can use regular or mid-grade fuel if you wish. The caveat here is that if you start to notice knocking/pinging, decreased fuel efficiency, and/or a decline in overall performance, you would do well to switch to premium fuel.
Premium vs. Regular: The Breakdown
Premium and regular are similar in that they both originate from crude oil and both are highly combustible. Where the difference starts to arise, however, is in the octane ratings. In general, premium fuel will have an octane rating of 90 or higher. The octane level is a factor in delivering maximum power while also preventing engine knock. Gasoline and air both need to ignite at a precise time for optimum performance. When they ignite before that time it's called "pre-ignition." It's this pre-ignition, then, that causes the condition we commonly refer to as engine knock. A fuel's octane rating refers to how well it resists pre-ignition. Because premium fuel has a 90+ octane rating, it is less subject to pre-ignition. Beyond that, premium fuel also has additives and detergents designed to keep your engine running optimally and causing less pollution.
Modern engines come equipped with computers that do a great job of adjusting ignition systems to play nice with regular gasoline, but only to a certain extent. When you use regular fuel in an engine designed to work best with premium, you can expect to notice compromises in both acceleration and fuel economy. The lower octane rating of regular also makes the vehicle more susceptible to pre-ignition. If you make the decision to use regular instead of premium for extended periods of time or under extreme driving conditions, you are setting yourself up for engine knock that could lead to more damage to spark plugs, valves, pistons, and other components. If a vehicle's knock sensor is picking up engine knock, it can adjust the spark timing to account for that even before you start to hear it. Still, that doesn't mean you should just forgo premium if a manufacturer calls for it.
So, you can sometimes get away with using regular in a pinch and not see much effect from it, but it's not a good idea to make this a routine. If you have any uncertainty on the matter, check your owner's manual; if it states that the vehicle requires premium, take it seriously. Trying to pinch pennies at the pump by opting for regular when your car really needs premium could come back to bite you when your car is in the shop for a condition your warranty may not cover.