IPA: /ˈhaɪpərˌmaɪlər/
KK: /ˈhaɪpərˌmaɪlər/
A person who drives in a way that maximizes fuel efficiency, often using specific techniques to save gas.
As a hypermiler, she always looks for ways to improve her car's fuel economy.
Hypermiler is formed from "hyper-" (meaning over or excessive) and "miler" (derived from "mile", which refers to a unit of distance). The term describes someone who drives in a way that maximizes fuel efficiency, going beyond normal measures to achieve the best mileage possible.
Think of someone who goes 'over' ('hyper-') the usual distance ('mile') to save fuel — that's what a hypermiler does.
No commonly confused words.