excessive oil consumtion 85 307

I just bought a 85 cutlass supreme with the 307 motor with 48000 miles. the car is in super shape plus the low miles. the downfall is that it uses oil some how. It smokes bad at first then it will get better then all of a sudden it gets bad again. it will spit oil out for a bit if it has sat for some time and smoke bad then it quits. i just pulled off the valve cover and it looks good the seals look good and the drains are clear. it will start up quick and run real good and i got 18 mpgs with it in the 160 miles that i drove it and in that time it used a jug of oil up. the spark plugs are brown but dry and have never fould out. the car runs really good but it just smokes. i also put some of that nosmoke stuff in the oil and it made it worse. And ideas????????