Is it possible to get higher gas mpg in RX350 by using premium gasoline ? It seems to, but don't know how it works and don't know how much more I get since one day is not the same as another.

Are there tests/science done to prove this?


  • What does the vehicle specs call for? Commented Jan 6, 2016 at 1:58
  • Most vehicles undergo Federal testing in the United States using premium and they are required to indicate that somewhere on a label the government requires to them to put somewhere. Commented Jan 6, 2016 at 2:35
  • the fed testing site says 18 city on regular but not info on premium
    – Victor
    Commented Jan 6, 2016 at 4:45

1 Answer 1


The only practical way of tracking fuel economy is driving duplicate courses for many tankfuls with each fuel. Complications like changes in seasonal air temperature, fuel type (Winter versus non-Winter gasoline), traffic, etc., all complicate getting a good picture of actual fuel economy.

For example, my commuter vehicle gets used almost identically for my weekly commute, and hardly at all on weekends, yet my MPG calculated at fill-up time varies by almost 2MPG. However on Winter gas it averages almost 2 MPG less than on non-Winter formula gas, but it takes several fill-ups to find the new average.

Premium gas only increases fuel economy in situations where the knock sensor invokes timing retardation while using lower octane fuel. If that condition is not occurring (and it's hard to tell if it is or isn't), then changing to a higher octane gasoline won't help.

If you tow, race, or accelerate up steep hills often, you may see a small increase in fuel economy.

Another complication in tracking fuel economy, is that it takes a little time for the engine system to "learn" that it has higher octane fuel. How much time depends on the system, and how often knock is occurring.

  • interesting to know that engine can learn
    – Victor
    Commented Jan 6, 2016 at 4:46

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