That is called blowby and it is normal on our trucks. One test that you can do to see if it is something to worry about is to run the engine and take the oil fill cap off and turn it upside down on the fill neck and see if if blows it off. If it doesnt there isnt really anything to worry about. If it does blow it off then you may need to look at getting a mechanic to look at the rings. You could have a cracked piston