Does my car really need premium gas? (octane)

Summary: Some auto companies recommend that you burn premium gas in your car. Some people use premium gasoline believing that the benefits are worth the extra expense. You may be able to save money on gasoline if you read this article.

Lately, it seems that just driving by a gas station and seeing the prices is enough to get your heart racing, the prices being as high as they are. But when you pull up to the pump with your $40,000 SUV you want to treat it right – you instinctively want to fill your baby up with premium. But do you really need 91% octane? And what is octane anyway?

Well, while this isn’t exactly rocket science, it is science, so pay attention. I’ll make it as painless as possible and save you money – be it at the pumps or your mechanic’s – in the long run.

Most cars today have a four-stroke internal combustion engine consisting of an intake, compression, combustion, and exhaust stroke. Without going into too much detail, basically a tiny drop of gas is mixed with air and a valve allows it into the engine, it’s compressed to make the upcoming combustion more powerful, the spark plug ignites, the compressed gas, explodes, and what remains leaves through the exhaust.

Octane – or octane rating – is how much fuel can be compressed before it spontaneously ignites rather than waiting around for the spark plug, when it should ignite. When compressed gas ignites on its own it causes the dreaded knocking and pinging that so many car owners complain to their mechanics about and that, over time, can cause serious (read: expensive) damage to your engine. The lower the octane rating, the less compression the fuel can handle before it self-ignites and the greater the chance of engine damage.

So how do you know if you really need the economy or the ultra premium? It used to be – and many say it still is – simple. Tom and Ray Magliozzi of the syndicated radio show and website Click & Clack Talk Cars, offered their succinct advice: “Use the manufacturer’s recommendation for octane. No more, and no less. Lower octane can cause pinging and overheating, which can damage the engine. And higher-than-required octane is simply a waste of money.”

But others disagree. According to an Associated Press article last month, the octane “recommendations regarding premium fuel are just that.” Martin Peters, manager of public relations for Porsche Cars North America Inc. even went so far as to admit that, “the car will run on regular fuel without damaging the engine,” and the higher octane is really just for “optimum performance.”

Sure, but if you drop all that dough of a high end performance vehicle, don’t you want it to, well, perform? While General Motors Corporation maintains that if you want your Corvette to act like one then only the highest octane will do, their spokesperson, Kyle Johnson said, “In most driving situations, you’re not going to notice it, like just driving around town or even cruising on the highway.”

Many people prefer to err on the side of caution, but the prices of gas being what they are lately, and the mileage the vehicles some of us drive get, going down an octane can significantly lower your gas bill over time. On the other hand, engines don’t come cheap. Since everyone has an opinion, be an intelligent consumer: ask your mechanic, check your manual, call your dealership, and go online to the manufacturer’s website and find out what your pros have to say.

4 thoughts

  1. Just read your advice about regular vs. high octane gas. I’ve been putting high octane into my ’04 PT Cruiser since I got it, figuring – you were right – that if regular is good, high octane must be better. Now, with gas prices going skyhigh, I’m wondering if I can switch to regular. Seems to me that some time ago I heard someone say that if you’ve started with regular, you really shouldn’t switch.

    Thanks for any advice you can give me.

    M. Waterbury

  2. Well, I’m still confused re. my 2003 BMW 5 series. Will I damage my engine with 89 or not??? Heard that if I blend 89, or even 87, and 93 the blends in the tanks are higher so I would come out with a higher blend than either combo and could still save some $$$. Any thoughts? The BMW was a special thing, not a run of the mill item for me so if I could save, it would be a good thing. thanks

  3. Required octane depends directly with the compression ratio of the engine in your vehicle. Higher octane fuel does not cause your engine to run hotter. It does have a higher flash point, which means it will withstand higher heat, and higher pressure before it ignites. That is the reason you need to use a higher octane gas with a higher compression ratio engine. People associate higher performance with higher octane because engines that need the higher octane(engines with high compression ratio) are high performance engines.

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