4.8is oil consumption and blue smoke at oil cap

[electricalserv x5]

Hi Guys , looking from the oil cap on my 06 4.8is with 69k miles on her.
1] should it be burning oil of a quart every 1500 miles? I notice the valves where rattling a bit too[ problem? only for 1500 miles]
2] check the oil today and there was blue smoke at the oil cap, it was a quart low, filed her up with syntech , all levels good.Could this damage the heads or engine ?
No black dust from exhust system. and rattle is gone. only been driving only 4 to 20 miles but have been try to put longer rides on her.........................
3] any one had any experience with this.............?