CLIENT

var lu = gta.tickCount;
function getDotProduct(x,y,z,x2,y2,z2)
{
    return x*x2 + y*y2 + z*z2;
}
function calculateMileage(veh)
{
    var mileage = (veh.getData("mileage") || 0);
    if ( gta.tickCount - lu > 250 )
    {
        lu = gta.tickCount;
        let matrix = veh.matrix;
        let vecMoveSpeed = veh.velocity;
        let speed;
        speed = getDotProduct(vecMoveSpeed[0],vecMoveSpeed[1],vecMoveSpeed[2],matrix.getElement(1*4+0),matrix.getElement(1*4+1),matrix.getElement(1*4+2));
        speed = speed*90;
        speed = Math.abs(speed);
        if ( speed > 0 )
        {
            veh.setData("mileage",mileage+(speed/3));
        }
    }
}
addEventHandler("onProcess",function(event,deltaTime)
{
    if ( localClient )
    {
        if ( localPlayer )
        {

            if ( localPlayer.vehicle )
            {
                calculateMileage(localPlayer.vehicle);
            }
        }
    }
});
addCommandHandler("mileage",function(c,t)
{
    if ( localPlayer.vehicle )
    {
        var mil = localPlayer.vehicle.getData("mileage") || 0;
        message("[#ffff00]Current car mileage: "+(mil/1000).toFixed(2)+" KM");
    }
    else
    {
        message("[#ff0000]You must be in a vehicle"); return;
    }
});