[Mariner]

If your vehicle calls for “regular”, know that it will get 10-15% better mileage on “premium”.

And your fuel intake system will last longer.

[zeebee]

If your vehicle calls for “regular”, know that it will get 10-15% better mileage on “premium”.

Entirely false and backward.

The more octane, the more additives equals lower percentage of fossil fuel.

You will get better mileage on less octane as long as your engine won't ping from valve clatter.