If I'm getting new wheels(19") for my 09 X sedan, do I need new nuts or OEM nuts can be used. Wheels are Enkei.

 

You will need new lug nuts. The Infiniti lug nuts are too big for most aftermarket wheels. Any decent tuner style lug nuts should work.

The Infiniti center bore is 66.1 mm, so you will also need hub rings. The Enkei wheels are likely a 73.1 mm center bore, so you will need a 73.1mm-->66.1mm hub ring.

 

I would say it depends on the rim. Enkei is a major OEM rim manufacturer so the aftermarket rims they make, depending on the style, may be compatible w/ your stock lug nuts.

FWIW, the Infiniti M45 sport rims are Enkei rims.