My Jeep is driving me crazy. while driving around town i have no problem. but highway...?

Well is it maybe your oil pressure relief valve is stuck closed and the pressure is fine at low rpm but when you get it on the highway and higer speeds the oil is just flowing to much at the top for it to bleed back down through the engine. thanks for the info on my car too i will have to try it. also if your engine has alot of blow by your pcv system might actually not be working ive had it where oil came out the dipstick before cause it was so bad. good luck

get a compression guage hook it to the spark plug hole and get the cylinder to top dead center on the comp4ression stroke. let it sit and see how quickly the compression leaves the cylinder slow loss is normal you but if it doesnt hold compression your compression rings are shot or maybe broke and your engine wont always smoke becouse the oil rings may still be doing thier job. test evey cylinder. had same problem on 4.0 jeep and drove for another year before i tore the engine down and found a single broke comp ring wasnt dispalced and the engine still ran good just blew oil every where and higher speeds more rpms more comp strokes more leakage

make sure the oil filler cap is there.i'm not kidding you might be surprised