It’s possible to disappear 1.5 quarts of higher viscosity oil with Lucas stabilizer in one week like this? Way In over my head with this.
I hate to to tell you this,but depending on your climate, how cold it is, Lucas stabilizer could contribute to the problem.
It's a massive thickener with no additives so I thickens your oil especially in cold weather. Oil that's too thick when cold , might not lubricate the valve guides ,wearing them out. combine that with the product diluting the oils add pack i.e. moly , zinc, etc.Then as the oil does get warm it goes right down the valve guides, especially when the engine vacuum is high. I.e. off the throttle coasting to a stop.
You don't see much smoke ,because the engine has enough compression to burn it cleanly. As opposed to worn rings where compression is low and smoke is evident.
I would try a set of valve seals first, after dumping the " stabilized oil ".
If that fixes the problem, use just motor oil from here on out.
If it doesn't, you may need to have the valve guides knurled or replaced. Either way, don't stabilize the oil.