Save Money and Stop Buying Premium Gas

Modern Engines Make Allowances for Lower Octane


  • Fuel Sign Picture

    Fuel Sign Picture

    Premium gas is typically 20 cents a gallon more expensive than regular. Your car will probably run just fine on lower-octane fuel. | March 09, 2011

3 Photos

When the price of gasoline spikes, drivers scramble to reduce fuel costs. A quick way to save at least 20 cents per gallon (often as much as $4 per fill-up) is to stop pumping premium gas and switch to regular grade. But how will you know if the switch is safe or if it will damage the engine in your car?

The key for drivers is to know whether premium gasoline is merely recommended or if it's required. In today's automobiles, advances in engine technology mean that even if the owner's manual recommends premium gasoline, the car will typically run on regular without issue and won't damage the engine in any other way. The car's performance might suffer only slightly: it might be a half-second slower from zero to 60 mph, for instance. But the average driver isn't likely to notice this drop-off.

Drivers used to buy a tank of premium gas every once in a while to clean their engine. Years ago, premium gasoline contained more detergents and additives to stop carbon deposits. But experts say that because of government regulations aimed at cutting emissions, all grades of gas, including those you buy at independent, low-price stations have plenty of additives to both protect engines and cut pollution.

Edmunds has compiled two lists: "premium recommended" and "premium required" for vehicles from the 2009-2014 model years (with a few 2015 model-year vehicles). If your vehicle is on the "premium recommended" list, you're OK to try switching to regular unleaded gasoline. If, on the other hand, your car is on the "premium required" list, then you have to run premium fuel. You can confirm the information on these lists by checking your owner's manual.

Smarter Engines Protect Themselves
If you're still in doubt about switching to a lower-octane fuel, here's a deeper explanation of why the change is unlikely to hurt your car.

First of all, premium gas is more expensive because it contains a higher percentage of octane. Why is this important? When vaporized gas mixes with air and fills the combustion chamber, it is compressed by the rising pistons. This makes the gas-air mixture grow hot and it could ignite before the spark plug fires, pushing backward on the piston. Higher-octane fuels can be compressed to a greater degree without self-igniting. That's why premium gas is used in high-performance engines.

In the old days, engines could not adjust to fuels with varying octane ratings. Use the wrong fuel and the engine would knock or "ping" audibly because the gas exploded prematurely. This knocking damaged internal engine components over time.

Today, engine control systems can compensate for low octane by monitoring knock activity and adjusting ignition advance to avoid knocking. This sophisticated electronic capability effectively tunes the engine on the fly and gives drivers more flexibility in the grade of fuels that they can safely use.

Compared to premium gasoline, lower-octane fuels don't allow the engine to run as much ignition advance during situations calling for rapid acceleration. More ignition advance allows the engine to make more power, and accelerate more quickly, during these conditions. Since the engine doesn't make quite as much power with lower-octane fuels, this translates into slower acceleration in cars for which premium fuel is recommended. The performance loss is especially noticeable in turbocharged gasoline engines, which have become increasingly popular in recent years.

The performance loss, however, is something you will only notice if you have a heavy foot and accelerate rapidly from a dead stop or while changing lanes at highway speeds. But if you accelerate moderately, the loss of power is barely noticeable, regardless of whether you use premium or regular-grade fuel.

When Premium Can Be a Money-Saver
Edmunds has noted, however, at least one case in which a car with a small turbocharged engine got better fuel economy when running on premium. The car in question was a 2011 Chevrolet Cruze LTZ and, perhaps befitting a car that's marketed as a money saver, the owner's manual only calls for regular unleaded gasoline. Yet in a specific test we noticed that we got better fuel economy (and ultimately saved a bit of money) by using premium fuel. One factor affecting the outcome of the experiment might have been that the testing was conducted in extreme hot-weather conditions, however.

If you want to see if you can save money by using premium gas in a car for which it's recommended but that doesn't require it, conduct your own test project. Monitor your fuel economy and performance over at least two tanks of premium gas. Record the trip mileage, gallons used, fuel price and octane rating in a notebook or in an app such as Road Trip or on a site such as Fuelly. If your car has an onboard fuel economy meter, make sure you reset it when filling up. Then, fill up on the same number of tanks of regular gasoline and record all the same data. Finally, compare the results. You're looking for a drop-off in fuel economy or a sense that the car is slower or hesitant under strong acceleration.

That's the drill for a premium-recommended car. You can stay with premium, or step down to regular unleaded if you want to.

It's a different story for a car whose engine requires premium fuel. The car will still run on regular fuel in a pinch, but you shouldn't make a habit out of it. The fuel's lower octane can result in elevated exhaust-gas temperatures and possible knocking, both of which can adversely affect the engine's health in the long run. Running regular-grade fuel in a car that requires premium might sound like a good way to shave a car's running costs, but the short-term savings won't come close to offsetting the cost of repairs to a damaged engine.

For those driving "recommended premium" cars, however, it's just a matter of driving moderately and avoiding acceleration with a wide-open throttle. Do that and you might never feel the difference between using premium and regular grade gasoline: and neither will your car.

Comments

  • famof3kids famof3kids Posts:

    Interesting Ford/GM/Chrysler have almost no cars that 'require' premium.

  • ianw33 ianw33 Posts:

    If you take the average difference of 20 cents between regular and premium, then multiply it by the average gallon size of a tank (15 gallons).... you would only be saving $3 per fill up by using regular. Not really worth it. You can save more by just driving smarter, or less. Fuel your car with what it was designed to be fueled with.

  • kalos kalos Posts:

    This article didn't discuss the simple expedient of using mid-grade gas. In many gas stations, the difference between regular and premium exceeds 30 cents. At least half of this can be recovered by using mid-grade or blending. Yes, I'll keep the $1.50 per tank difference. Engine performance and mileage probably doesn't suffer at all.

  • rdaex1 rdaex1 Posts:

    Lets try to focus on more fuel savings ideas that may ruin your car! 1) Drive 50 in the fast lane, slow and steady saves fuel!! Just dont get run over! 2) Take corners as fast as possible to minimize the need for acceleration 3) Coast through red lights, eliminating more acceleration Seriously edmunds.. youre better than this

  • guillermoii guillermoii Posts:

    Why was Suzuki not on either list? And the simple Honda Civic 4 cyl REQUIRES premium? I question your list. Using regular gas just won't give you the added octane to give you the boost the car was designed to have. REQUIRED is a market ploy.

  • centurion3 centurion3 Posts:

    Great article. With my 2010 Mini Cooper S, I was wondering about the grade of fuel. Now I know. Thanks.John K.

  • Fiifi Fiifi Posts:

    What the hell, so I click on the link to see the chick and she's no where to be found. I see what you did there, Edmunds! Not funny, I tell ya, not funny at all!

  • kunk2 kunk2 Posts:

    E-85 Good Idea, But it's price so what you save in money you lose in miles per gallon. So why use it. E`85 Why does it go up the same as gas? Only 15% of it is gas. If it was worth it to use people would use it. When people start using it, more work for people. The president said we have to create our own energy. Well isn't E-85 new energy. Why does it cost so much. (GREED) again.I e-mailed the E-85 people last year and wrote back that it's the retailers who set the price not them. All I know if the price was half what gas is MILLIONS of people who have flex fuel cars and trucks would be using it. After all it's 105 octane so there is no loss of power. The government needs to step in so they STOP killing us while new ways are developed.

  • igilson igilson Posts:

    Saving money IS NOT CORRECT!! and E-85 is a waste of money. My car gets 8% better gas mileage on premium versus mid grade and 12% better than low grade. Gas cost $4.15 low grade and $4.35 premium in S.Cal 4.15 times 1.12 is 4.65. So I use premium AND SAVE MONEY, !!!! I save $4.80 a tank and the car runs better. E-85 gets 30% less mpg than gasoline. The price of E-85 (where you can buy it) is $4.65. The gas equivalent price is over $6.00 a gallon. The futures price of ethanol is available in most newspapers. That is what drive the price of E-85

  • alhajikdabo alhajikdabo Posts:

    The average national retail price of premium self-serve gasoline currently is topping $3.78 a gallon. Fuel costs are leaping by nearly 40 cents a month. And drivers who are pumping premium are undoubtedly asking themselves if they can safely switch to regular, which is about 20 cents a gallon cheaper..... engine 2.5

  • meyrick007 meyrick007 Posts:

    i don't get why a g37 coupe is under RECOMMENDED and a g37 sedan is under REQUIRED when both engines are the same.... confused here...

  • markn6 markn6 Posts:

    If premium gas is 20 cents more and you get 3 mpg better gas mileage, based on a 15 gallon tank and 25-28 mpg. you could get and additional 45 more miles for only $3.00 more. Sounds like a deal to me.

  • dtru dtru Posts:

    I thought this site gave trustworthy advice... I was wrong. Use the octane that your manufacturer RECOMMENDS. Why would you listen to anyone else other than the people who engineered your engine? Example: Dodge recommends 89 but you can use 87. When you use 87 it reduces timing which hurts performance and MPG. So using 89 and in some areas 91 if the gas quality is low, will actually give you higher MPG which ends up saving you more money then using 87.

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