blow by
Since I am the one that posted that, I guess I should go to a bit of detail as to why I made the statment. First, I agree with all the post here as to 'not to worry'. Our engines do definitely breath with the normal stroking of the pistons. The six cylinder is very smooth as to crankcase pressure from the piston movment but there is some palpitation. RPM, oil level, winter summer, and how the engine is used all play a part in the pretty normal consumption of a small amount of oil. As the engine ages, there will be more and more 'normal' escape of compression gasses that occurs. As long as the cylinders are in good shape and the rings are not scuffed, very little will escape there. More gasses will be coming from the valve stems and turbo than from the cylinders. (And certainly no one ever raises the turbo pressure to increase the possibility of leaks at the stems. )
BUT, I made the statment from personal experience on a truck that I bought about two years ago. Thinking that since the truck only had about 160k miles, it couldn't have anything wrong with the engine. I drove the truck, noticed brake problems and was satisfied with the power level. The transmission worked fine and the tires were shabby. I noticed that the truck had a new water pump. Really decent paint and super clean interior. Cranked instantly just as you expect the first genner to do. Also noticed that the vent pipe had what I thought was too much discharge of gasses. Still I figured it just need a good work out. So I made an offer, bought the truck and drove it home. In fact drove it around for a couple of weeks not running it very hard. I worked it a little and still no improvment in the blow by. Now we are talking about real blow by and not just a little venting.
The net result when I pulled the engine down was that it had scuffed the number six cylinder and it required a complete overhaul. Needless to say, I didn't really come out on the purchase. Doing all the work myself, I am still ok but had it required a shop overhaul, I would have been really stung.
So, if you are looking at a truck that you know nothing about, be critical of a stream of gasses from the vent pipe. It could be grief. Still, price is the final factor.
James