Gas Mileage

I get great mileage....if all hiway, the highest I have gotten was 26.1 (use Texaco hi-test, or shell..other brands I get significantly less) with moderate city driving last tank was 23.4....these numbers went up since changing plugs, just replaced with same stock platinums....was getting around 22, so I am sure plugs helped....the old ones had about 50k miles on them, so were definitely ready....I am easy on acceleration, so my style is conducive to high mileage.....I use Valvoline 5-30 regular dinojuice and change at 3000k miles