ISI are running a special promotion on rFactor 2 this weekend as they offering the game for 20% off its usual price if you use the promo code RF2BRAZIL20.
If you're unsure on the game there is a demo version available and you also have a 1-time 7-day return policy if you find that the game isn't right for you after purchase.
They have recently added the Brazilian circuit, Interlagos, to the game and the discount is to celebrate this fact.
It should be noted however that the promo code RF2BRAZIL20 is for New purchases only.
You can order your copy of the game here.