When Premium Gasoline Is A Waste Of Money

Last year AAA reported that Americans waste billions of dollars each year on premium gasoline. A new AAA study concludes that’s true in most cases even if premium-grade is recommended for your car.

If you are like many Americans, you may occasionally treat your car to premium gasoline. You might not be certain whether it helps, but it can’t hurt, right? Maybe not, but you just might be throwing money down the drain.

Last year I reported on a study by AAA that concluded American drivers had wasted more than $2.1 billion during the previous year by using premium-grade gasoline in vehicles designed to run on regular fuel. Now AAA has released new research findings that tested vehicles for which premium-grade gasoline was recommended but not required.

Together with the Automobile Club of Southern California’s Automotive Research Center, AAA tested vehicles that recommend the use of premium (91 octane or higher) gasoline. These vehicles were tested under extreme driving scenarios such as towing, hauling cargo and aggressive acceleration. AAA’s tests under these conditions showed:

  • Fuel economy for test vehicles averaged a 2.7% improvement. Individual vehicle test result averages ranged from a decrease of 1% (2016 Audi A3) to an improvement of 7.1% (2016 Cadillac Escalade).
  • Horsepower for test vehicles averaged an increase of 1.4%. Individual vehicle test result averages ranged from a decrease of 0.3% (2016 Jeep Renegade) to an improvement of 3.2% (2017 Ford Mustang).
  • According to national averages, the price difference between regular and premium gasoline is approximately 20% to 25% — about $0.50 per gallon.

AAA concluded that the vehicles tested are unlikely to see any benefit from using premium gasoline during typical city or highway driving. But even if someone consistently drives under the extreme scenarios tested, a 2.7% fuel economy improvement won’t justify paying 25% more for premium gasoline. Thus, the conclusion is the same as the conclusion from last year’s research — Americans are mostly wasting their money if they are buying premium in this situations.

Of course, if a vehicle requires premium, that’s a different matter. Higher-octane fuels are more resistant to pre-ignition, which allows them to be used in engines with higher compression ratios. That enables higher performance and higher fuel efficiency than in engines with lower compression ratios. Using a lower-grade fuel in such an engine can result in knocking and pinging as the fuel ignites too early, and this can damage the engine.

Note that premium gasoline doesn’t necessarily contain any more energy or any better additives than cheaper gasoline. So unless you have a vehicle that requires premium gasoline, you are probably wasting your money if you are buying it. AAA’s newest research shows that’s true even if premium fuel is recommended for the vehicle. But if you switch to regular and notice an engine knock, then you should probably stick with premium.

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3 thoughts on “When Premium Gasoline Is A Waste Of Money”

  1. Mazda SPCCI ignition system sure lifts the fuel efficiency bar. This compression ignition (diesel) system is the much sought after lean burn system for one half the fuel and low NOX emissions. This would fit in nice with variable compression. It is amazing how much torque can be produced with modern small engine technology. Also, how they can vary the torque for the horsepower demand. With this new compression ignition technology an engine can deliver efficient minimal torque and good efficiency. This is the range most often the car operates within. Also, with high turbo and air compressor equipment the engine can be pushed to 2-4x more power when needed. The problem is the fuel or the fuel is turning out to be the weakest link. These engines need consistent fuel attributes to tune to and they need much higher octane. Good to have this fuel character, but I guess that is impossible without a very expensive price tag. Then the problem with utilizing more hazardous chemicals to make it so.

    1. I have heard talk by engine designers that a super-premium gas would be really helpful in meeting future CAFE standards. Then I hear from the refiners that having multiple grades and winter-summer fuels adds a lot of cost. So I am not sure there is enough push yet to change the status-quo.

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