There is a belief that filling a tank with higher-octane gasoline automatically reduces fuel consumption. People imagine swapping 92-octane for 95, and then 95 for 98, with the fuel economy improving at every step. The reality is not so straightforward, and the idea often fades in practice as the engine adapts slowly to the change.
Experts at a long-standing automotive publication in Russia note a key nuance: the benefits of higher-octane fuel do not appear instantly. The transition to a higher grade can take time, and the outcome depends on the engine’s state and how long it has been operating with the previous fuel, rather than on a single tank fill.
In practical terms, running a vehicle on higher-octane fuel at a single service station for a short drive will not magically unlock significant gains. A heavily carboned engine may see a temporary improvement as deposits are slowly cleaned during an extended period of using the upgraded fuel, but this effect is gradual and not guaranteed to restore the engine to its original performance, let alone all the way to a perfect baseline.
When comparing two new cars—one running on regular gasoline and the other on higher-octane fuel—the results tend to align in both power and efficiency. Expect similar performance benchmarks and similar official fuel-economy figures during standard tests, even if one uses a higher grade fuel for the experiment. The changes, if any, are not dramatic enough to defy the published specifications or the typical bench-test outcomes over the short term.