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Money Leaks: Buying Premium Gasoline

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Imperial Gas PumpI have a friend who absolutely loves his car. It’s not a fancy car, it’s just new to him and he treats it like his baby. He takes very good care of it, gets it washed once a week (more if he gets it dirty), and is generally a very caring owner. He also fills up with premium gasoline because, well, he thinks the gas is “better.” The only problem is that, just like his once a week car washes, he’s leaking money like crazy. While it’s debatable whether or not you really need to wash your car once a week, it’s almost certainly a leak if you go to a car wash, putting premium gasoline into a car that doesn’t need one is completely unnecessary. It’s as bad as putting regular unleaded into a car that demand premium.

Is premium gasoline better? “Yes.” Yes is in quotes because it’s better at handling compression. The higher octane means it can be compressed more before exploding. Cars that require premium gasoline will compress the gasoline to much higher PSI before igniting it. If you put regular unleaded into a premium gasoline engine, it’ll misfire. The fuel will ignite before the engine is ready and that’s the reason you’ll hear “knocking.”

This is the latest edition of our Money Leaks series.


When you put premium gasoline into an engine designed for regular unleaded, it’s like NFL playoff-bound teams playing their starters in the final game of the regular season. There’s no added benefit to using the better stuff, it just costs more. Your car doesn’t run better, it doesn’t run more efficiently, it simply costs more for the gasoline. Higher octane doesn’t not mean better fuel, it’s just different fuel that’s more expensive to manufacture.

If you want to treat your car better, avoid driving like a maniac, which increases wear and tear (and carpool!).

(Photo: robbn1)

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13 Responses to “Money Leaks: Buying Premium Gasoline”

  1. gharkness says:

    In addition, if you have a car that “requires” premium fuel….give regular a try. I drove two Acuras for 3 years each on regular fuel, and neither one of them EVER knocked, not even once. Mileage was excellent, too.

    But just to be sure, when I bought my latest vehicle, I bought one that is rated for regular fuel. Spending more on gasoline is something I have no interest in doing!

    • eric says:

      I drive an Acura too and because the manufacturer says to pump premium, I pump premium in my car. I’m not saying it’s right or wrong, but I trust that the company that made my car would know what’s best for it. Just my opinion though.

  2. Landon says:

    So true! Here in Iowa, super unleaded is subsidized so it’s actually cheaper than regular unleaded by .10 cents. I still see people use regular though, but it’s pointless because you’re getting a higher octane for less here in Iowa. I wonder why we even have regular unleaded here since 89 octane is cheaper than 87. Premium is still most expensive, but my Cobra needs it because of the supercharger and higher compression.

    My grandpa uses super unleaded in his Cadillac which requires premium, but it has knock sensors which retard timing I guess and he doesnkt drive it hard so it doesn’t hurt, but I still tell him he outta use premium.

  3. attgig says:

    regular in a car that requires premium won’t knock (in most modern cars), but you won’t get as much horsepower from it, and you may also lose some fuel efficiency from it. it can also lead to other issues that will get your check engine light to come on…

    • Bored SysAdmin says:

      +1. For cars designed for regular, but adding premium like author said – not going to do a thing, unless you take to garage for adjustment – then you could get some savings – using less fuel, but it would not add more boost, unless you drastically change the engine with much better air flow

  4. We recently bought a Lexus SUV which does call for premium, but after discussing the issue with my car-savvy uncle, he also agreed that regular would probably work just fine. We kind of split the difference and have been buying mid-grade, and we haven’t run into any problems.

  5. Stelios says:

    WHat attgig is the correct answer. If the engine requires premium it is becuase of the design. Yes modern ECUs can handle retardation to stop knock but yiou will lose power and lower your fuel economy. And I would be wary of doing that long term.

    Bottom line, if you vehicle does not require higher octane fuel, it is a waste to do so.
    If it does, you should. Dropping by a few mpg is a lot more expensive than saving 10-15 cents per gallon for the cheaper fuel, if nothing else, even if you are not concerned about the engine’s longevity and health.

  6. Aaron says:

    You should always follow the recommended guidelines for fuel in your car. If it says regular, use regular. If it says premium, use premium. If you downgrade your fuel because you *think* it is ok, you are taking an unnecessary risk that could cost you much more down the line. Internal engine problems are notoriously difficult to fix because one failure inevitably leads to others, which warranties won’t cover if you aren’t using the recommended fuel. There is so much more than simple compression ratio when you are dealing with fuel such as, engine block material, ignition and timing, cooling, etc. There are many ways to pinch penny’s but compromising fuel is not one of them. That said, I think that the main focus of the article is correct, if your car doesn’t require premium then don’t use buy.

  7. govenar says:

    Shell seems to say that they put more cleaning agents in their premium gas, so it might have more benefit than just higher octane, though it probably doesn’t matter for most people.

    • Aaron says:

      I have a close friend who is an engineer at Shell. He explains that in it’s base form all gas is the same. Crude oil is refined to be 87 octane, 89, etc. Afterwards, each major gasoline provider adds additives, a.k.a ‘Cleaning Agents’ to their blend of gas. Shell, BP, Mobil, it’s all pretty much the same. Kinda like OJ and OJ w/Calcium. Nice to have the calcium but that is not why I’m buying OJ nor am I relying on it for my source of daily calcium Same with gas, there should be no brand loyalty because it quite frankly doesn’t make sense. In fact if you have an off brand gas station, it is usually significantly cheaper, yet they get the gas from the same refineries. Days of shady gas station pumps was like 20+ years ago. All are randomly tested by your states weights and measures dept.

      • PeterM says:

        The thing that amazes me is that no matter what the price of gas, premium is always pretty much 20 cents more. So, this summer when gas was four bucks a gallon, premium was only 5% more than regular. Compare that to years ago when regular was a buck and premium $1.20, a whole 20% more. If the prices went up proportionally, they would be more like $4 and $4.80, respectively.

        The way I see it, for a car that recommends premium, the higher the price of gas, the less rational it becomes not to use premium. Consumer Reports testing indicated for a car that does not require premium there is no mileage gain or performance improvement to using premium, but for a car that requires premium, not using premium could reduce fuel efficiency. The question is how much?

        My european wagon requests premium but seems to run fine on regular–I’ve never heard it ping. I’ve tried to run tests by using the onboard computer to tell me the average mpg over three or four tankfulls of either grade of gas. As far as I can tell, I can get about 1 mpg better mileage with premium, maybe. The car seems to average about 20mpg with regular and about 21mpg with premium. This was not a controlled experiment, just averages over a couple of months of pretty much the same type of driving so it is possible that the difference is due to other factors. In any case, that’s a difference of 5%, about the same difference in cost between regular and premium, so perhaps it’s a wash.

        On a more serious note, what if the tanker truck accidently fills the tanks with the wrong grades, premium into regular and regular into premium, assuming that it is possible. The fuel has mixed with what was left in the tanks so they really can’t correct the mistake. That would mean that regular is always regular or something better. But premium might be premium or something worse. Hmmm.

  8. Tim says:

    I’ve often wondered why we need three levels anyway. Regular for most of us, premium for those who require it…cut out the middle and save on extra shipping,storage, manufacturing, processing, refining etc = cheaper gas for all?

  9. FrugalRandy says:

    According to the Federal Highway Administration, the average American drives about 13,000 miles per year. If a car gets 20 MPG, then it will use 650 gallons of gas per year. With a difference between regular and premium at $0.20, this results in a difference of around $10 per month for an average driver.

    Cars ARE designed for specific fuel and oil types, and if your owner’s manual requires or even strongly suggests using premium, then you’re foolish to buy otherwise just to “save” $2.50 a week. Likewise, if the vehicle does not specify premium, it is equally inefficient to fill up with premium.


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