oil filler tube

I was just wondering... with my truck at operating temp & at idle, if I take my oil filler cap off there is very slight pressure coming out it seems. mist like smoke comes out. put my hand over it & cannot really feel pressure it's just a slight amount. no blow by from tube next to oil pan. is this normal? had inframe done 35,000 miles ago. using or leaking 1 gal every 3000 miles.

 

I have the 11.1 ser 60 after inframe I had hauled 75-80,000 gross wt.I was told to work the engine. I id not idle or lug engine in break in period. I have heard some engines after inframe will be a oil burner. I am not sure what that depends on. one reason why I had inframe done was the oil usage. after over 1.3 miles, I knew the rings had to have some wear, not to mention all the other components. it did use more oil before the inframe, but a gal every 3 grand to me is eccessive.

I've had unusualy good luck out of this engine, over 11 years now & even after inframe, it has the original turbo. the cam was not replaced during rebuild. it was good as new. the bottom half & the gear train was imspected & in no need of replacement. though the bottom was done with the inframe kit. just saying the shop said the bearings, e.t.c. looked like vitually no wear on them. truck never saw rpm's over 2000. did not lug. always changed oil, evey 10,000 I took extremely good care of the maint part of the truck. I will be by the shop some time next week that done the inframe. will ask them, just thought I would ask here in the meantime. thanks for the replies.

 

I will say that after inframe I changed the oil 1st time at approx 5 thousand miles, second time 5 grand, 3rd time 7 g's 4th 8 so on. & will resume my ole habit of changing every 10,000 miles.