Answer by
LeheckaG (1826)
Gasoline's-octane-rating can be increased by mixing high-octance-additives into your-gasoline,
which is what oil-refineries/terminals do when blending higher-octane-gasolines.
Higher-octance-gasoline decreases "knocking" or early/pre-detonation
(especially at higher-speeds/operating-temperatures),
but does NOT necessarily increase fuel-economy/gasoline-mileage
(unless you race/speed all-of-the-time).
For better-fuel-economy:
Change your-air/oil-filters & grease/lubricate-bearings;
Get an-OBD-II-code-scanner
(some have real-time-fuel-economy-statistics)
to find accelerator-pedal/speed/transmission-sweet-spot;
Accelerate-slowly/maintain-CONSTANT-speed/COAST/decelerate-slowly/brake-sparingly.
