Fractional distillation of crude oil and resulting fuel ratios
Crude oil is a complicated mixture consisting of a variety of different hydrocarbons and the particular composition is very variable depending on where it is found.

Distillation is merely a means of separating those components so it can do nothing to create more of one of them. And gasoline is, essentially, just a mixture of those components with similar properties and boiling points. There is little you can do by distillation to create more gasoline.

However refiners do have access to chemical means to alter the composition. Catalytic cracking, for example, converts constituents into different chemicals and this can allow a refinery to create more gasoline or diesel by breaking down the higher-boiling components into smaller parts. But this is much more complicated than distillation.