Do I need to use premium gas?

Posted on June 8, 2022 in Tips From The Pros

With gas prices on the rise, it's important to consider how your car-related expenses will change. One of the biggest expenses of owning a car is fueling— and if your car takes premium gas, that can be a big disappointment. Premium gas can cost significantly more than regular gas depending on where you live, and a lot of customers ask us: can you skip the premium gas for a while when prices get too high? We have the answer.

Why Premium?

Regular gas has an octane level of 87, while premium gas usually has an octane level of 92 or 93. The higher octane level is designed to prevent knock in engines with high compression ratios-- or the volume inside the cylinder that is displaced when the piston moves. If you use low-octane gas on a car with a high compression ratio, the gas can ignite prematurely, creating knocking and rattling noises in your engine. A mild knocking sound isn't usually worrisome, but it's definitely not ideal; and a consistent, heavy knock could damage your engine. Fortunately, few cars actually require premium gasoline these days-- for the most part, it's just the luxury cars that do. The majority of cars have engines with a lower compression ratio, so low octane gas is more than adequate to power the engine. 

"Recommended" vs "Required"

The best way to find out what kind of fuel your car requires is to simply look in the owner's manual. But this is where it can get tricky. If your car requires premium gas, then you need premium gas— no question. Your car has a high compression ratio and moving to a lower grade will likely cause knocking, which you really don't want.  If your car recommends premium gas things get a little murky. In some cases, you can switch to a lower octane without risking engine damage but mixing gas types is not recommended. If you'you will notice a drop in performance. Some proponents of premium fuel argue that the level of precision it provides can make it easier to merge on the freeway or avoid an accident. Some say it can also improve your mileage, but again: you'll have to measure your mileage before and after against the increased cost to see if it makes a cost-effective difference.  A lot of newer cars now have internal knock sensors that change the game-- they can adjust the engine's timing to prevent knock which allows you to use lower octane gasoline if you so choose. 

So... do I really need to use premium fuel?

In the end, the answer is pretty simple: read your owner's manual and do what it says. In many cases, the answer is probably no -- you'll likely be able to use regular fuel with no noticeable issues except for minor losses in performance and gas mileage. If your owner's manual says that premium fuel is required, then you should do it, but your car won't blow up if you occasionally opt for regular. If you have doubts or questions about the instructions in your owner's manual, you can check out the Federal Trade Commission's fast fact sheet for more info on the benefits of high octane gasoline, and the laws surrounding it. The important thing to remember is that engines running on less combustible fuel are less likely to experience pre-ignition than powertrains that run on more combustible regular gas. Pre-ignition leads to engine knocking; too much engine knocking can cause damage, and it certainly means that your engine isn't running very well... which isn't something you want to deal with after buying a car.

At V&F 

At V&F, we strive to provide our customers with a well-rounded knowledge of all things automotive.  Since 1988, our family-owned and operated service center has been providing top-quality auto repair services to Agawam, Feeding Hills, Southwick, West Springfield and the surrounding Massachusetts communities. If your car needs maintenance or repair, call us at (413)314-2280 or schedule an appointment online. This article was originally published in 2019 and has been updated to reflect current trends.