Accessing embedded type fields through interface

It seems like I missed something important but I can not figure out what it is. I use reflect to access embedded type fields through an interface. The problem I have is that according to runtime/pprof it eats up a lot of CPU. I do not like to implement Setter and Getter methods on all Vehicles so is there a better way of doing this?

Simplified sample:

package main

import(
    "reflect"
    "fmt"
)

// the "contract" is that all vehicles have an embedded Engine
type Vehicle interface {}

type Engine struct {
    Power float64
    Cubic float64
}

type Car struct {
    Engine
    Weight float64
    TopSpeed float64
}

// more Vehicles with Engines here...

func EngineCheck(v Vehicle) {
    // this does not work:
    //power := v.Power
    // reflection works but eats up a lot of CPU:
    power := reflect.ValueOf(v).Elem().FieldByName("Power").Interface().(float64)
    fmt.Println(power)
}

func main() {
    c1 := &Car{Engine{120.0, 1.2}, 1.5, 250}

    EngineCheck(c1)
}