public function ensureCorrectGear(Engine $engine, $speed)
 {
     $engineSize = $engine->getSize();
     $turbo = $engine->isTurbo();
     // Some complicated code to determine correct gear
     // setting based on $engineSize, $turbo, $speed etc.
     // ... omitted ...
     return "Working out correct gear at {$speed}mph for a SPORT gearbox";
 }