Cars That Require Premium Fuel Don't Always Benefit From It, Our Tests Show
We compared fuel economy and acceleration in two very similar SUVs—a luxury model that requires premium, and a mainstream one that doesn't
- Consumer Reports testing found virtually no measurable difference in acceleration or fuel economy between two luxury SUVs from the same brand that require premium gas and their mainstream counterparts that use regular 87 octane fuel.
- An SUV that requires premium gas can cost more than $3,000 in extra fuel costs over five years of ownership due to the price gap between octane grades.
- Automakers often push premium gas requirements to achieve higher performance specs that the average driver might not notice.
- Even cars that don’t require premium can confuse drivers with unclear fuel guidelines in owner’s manuals.
- If your car requires premium, use premium. But if it only recommends premium, it’s safe to use regular in most scenarios.
This is a story of two SUVs. Even though they have different badges on their hoods, both share the same basic design, use many of the same parts, and get the same EPA combined fuel economy rating. Both get good ratings in Consumer Reports’ extensive road tests, as well as our reliability and owner satisfaction surveys. They are even powered by slightly different versions of the same engine. But only one of them could cost you hundreds of dollars more at the gas station each year because it requires pricier premium fuel.
Photo: Toyota Photo: Toyota
Only a few of these are sports cars, such as the Chevrolet Corvette, which often require premium fuel to handle the stress and heat of high-performance driving. The rest are luxury SUVs from Audi, Volvo, and others that are more likely to be driven around town, not around a track.
“A handful of high-performance vehicles truly benefit from premium, but some automakers are using premium fuel to squeeze extra horsepower out of family haulers,” says Fisher. “It’s often for bragging rights rather than any consumer benefit.”
The added cost of requiring premium gas is a particular concern for used-car buyers. On paper, used luxury vehicles may appear to offer more for your money because they tend to have more features and depreciate faster than mainstream models. However, higher operating costs can negate those savings: On average, premium fuel costs 25 percent more than regular.
As gas prices continue to eat into household budgets, the experts at Consumer Reports say that automakers should avoid designing vehicles that require premium unless it’s absolutely necessary for specialized vehicles, and that they should use clear language to explain which fuel to use.
Photo: Lexus Photo: Lexus
“In our testing, we couldn’t quantify additional performance or refinement... but the average consumer will notice the hundreds more they’ll be spending on fuel every year.”
Senior Director of Consumer Reports’ Auto Test Center
Engine design matters, too. For example, Toyota and Lexus largely replaced the six-cylinder engines used in older versions of their SUV lineups with turbocharged four-cylinder engines. Smaller engines and higher compression ratios lead to higher temperatures, which increase the risk of knock. “As you reduce the size of the engine and introduce turbocharging, knock becomes increasingly more of a problem,” says Giorgio Rizzoni, director of the Center for Automotive Research at Ohio State University.
Similarly, to get more horsepower out of an existing engine design, automakers can make small changes to valve or ignition timing, which can increase the risk of knock. “It’s simply because of some engine control parameters that have been changed to give the engine some extra power,” says Rizzoni.
If premium fuel is necessary to match the horsepower, acceleration, or towing figures used in advertisements and listed on spec sheets, the manufacturer will likely tell owners to use it all the time. “The manufacturer will say you must use premium because they don’t know how you’re going to use the car,” he says.
Manufacturers may require premium even for cars that are rarely driven at their limits, such as luxury SUVs that aren’t set up for towing. “Most cars aren’t driven at wide-open throttle, but that’s where your horsepower and acceleration numbers are recorded,” says Prucka.
Photo: John Powers/Consumer Reports Photo: John Powers/Consumer Reports
| Vehicle | Toyota Grand Highlander | Lexus TX350 |
| Engine | 2.4-liter 4-cylinder Turbo | 2.4-liter 4-cylinder Turbo |
| Engine Code | T24A-FTS | T24A-FTS |
| Horsepower | 265 hp @ 6,000 rpm | 275 hp @ 6,000 rpm |
| Torque | 310 lb.-ft. @ 1,700-3,600 RPM | 317 lb.-ft. @ 1,700-3,600 RPM |
| Compression Ratio | 11.0:1 | 11.0:1 |
| Bore x Stroke | 87.5 x 99.5 mm | 87.5 x 99.5 mm |
| Displacement | 2393 cm3 | 2393 cm3 |
| CR 0-60 Acceleration | 8.0 | 8.1 |
| CR Overall Fuel Economy | 22 mpg | 21 mpg |
| Fuel Requirement | 87 octane | 91 octane |
Photo: Toyota Photo: Toyota
For example, some Audi vehicles say that if regular is used, “the vehicle should only be driven with low engine load and in the middle of the RPM range.” Alfa Romeo differentiates between “light” and “heavy” knocking. Nissan says its Z sports car can be “partially filled” with 87 as long as it isn’t driven hard and as long as drivers fill up with 93 or higher as soon as possible. Mercedes-Benz says owners can “temporarily” use 87, but doesn’t specify for how long. Similarly, Porsche allows for “emergency” use of regular fuel in some vehicles.
Some cars have labels that mix and match the RON scale for octane measurement, which is not used in North America, with the (R+M)/2 scale used in the U.S. This may confuse owners into purchasing a higher grade of gas than their vehicle needs.
“We’re calling on automakers to be clear about what a car needs in language that the average driver can understand,” says Fisher. "To know what it costs to run your car, it’s not enough to just know the fuel economy, but what that fuel will cost you."
What Can Car Buyers Do?
In the meantime, if you’re shopping for a vehicle, whether new or used, consider a mainstream vehicle instead of a luxury one.
A hybrid vehicle’s fuel savings might offset the extra cost of premium, and the design of some hybrid powertrains makes them less likely to require premium.
That’s because hybrid powertrains use an electric motor for extra power under heavy acceleration, which is when an engine is at the highest risk of knock. “You can have the performance, but it doesn’t have to depend on the fuel anymore, because the electric components of the powertrain give you that instant boost of torque,” says Rizzoni.
If there’s no hybrid version available or if you already own a vehicle that requires premium, we recommend that you stick with what the manufacturer says to do and budget accordingly.
“If your car requires premium, use premium,” says Fisher. “If it only recommends premium, it’s safe to use regular unless you experience knocking, or if you’re putting the engine under heavy stress.”
