[chroma]

Different states have different requirements for gasoline and that seems to work just fine. Gas in California has higher ethanol content than most states. Oregon requires that someone else pump your gas. All the states have different taxes on gasoline. Yet you can gas up in one state and drive to another without issue.

[nameless912]

Because cars have been designed to deal with it since the 80s at least. Airplanes not so. Sure, we could begin to manufacture airplanes with more tolerance for different gasolines (and in fact we have; many modern high compression aircraft engines can take unleaded car gas), but it's taken decades to get to even this point.