As already mentioned this is a common problem with Toyota engines of this era (98-02). I believe it had to do with the oil return holes being made too small and clogging up with carbon. Which results in the rings sticking. Your cat might be soaking up most of the smoke for now.
Additives may or may not help. Most are gimmicks. Aside from tearing down the engine and physically cleaning those oil return holes, you’ll find it’s an issue you’re just gonna have to live with. Using thicker oil might slow down the consumption
I’d also double check the condition of your coolant. Make sure it isn’t milky, which would be an indication of a bad head gasket. Unlikely, but best to double check.
I would put in 20w-40 and forget about it. In fact, at the rate it is burning, you never need to change the oil, just replace the filter every 3K or so miles, and you are golden.
If the supply tube to the valve cover is dry, that means the PVC system is working. If you were burning oil at the rate you are loosing it, the blowby should overcome the PCV system and the supply hose would be wet with oil.
I suppose that if the oil control rings were stuck and pumping oil into the combustion chamber but the compression rings were good, then I guess you could burn oil without getting a lot of blowby, but I have never seen it. The burning oil would gum up the compression rings in short order and they would start sticking and stop sealing.
If the oil drain holes were plugged, its a simple fix which is to remove the valve cover and use a thin screwdriver to clear the holes. A quick check would be to check the oil level with the engine is running. If the oil level is normal with the engine off, and the drain holes are clogged, the oil level would drop significantly with the engine running, significant meaning more that 1/2 qt.
All these engines are known for front seal leaks, both the 4AFE and 1ZZ series will leak from the front seals, but they usually will be seen on the driveway. One leak that can go undetected if you don’t idle the vehicle in your driveway very long would be the oil pressure sending unit. It would send out a very fine mist that would be almost like a smoke. If there is nothing for the mist to hit and condense against, you would not see it. The best way to detect this is to wrap a piece of paper towel around the sending unit and drive it for a little while, If the paper towel becomes soaked in oil, this is your leak.
One more trick I have seen for oil control rings is to remove the spark plugs and pour in a capful or two of Seafoam or Breakfree oil. Breakfree works better but you may need to go to a gun store to get it. Let is sit over night, then crank the engine a few times to expel as much oil as possible before replacing the plugs. Breakfree burns without leaving any residue behind which is why it is used on guns so I would really recommend this oil for cleaning the rings.
I don’t know if this really works but I have heard a lot of people swear by it so it could be worth a try.
I had stuck rings on my boat, and my boat guy said yamaha ring free is the best. Still poor compression in 1 cylander, as always, but has been running like a champ and was probably that way when I bought it years ago, 86 motor. AHave you done a compression test, or leakdown test? Good place to start I say.
DocNick stole the words out of my mouth… With so few miles in such a long time… I would suspect blow by from stuck piston rings.
You can find MANY products that actually DO WORK to free up stuck piston rings. They are in EVERY large auto parts/accessory stores like Auto Zone, Pep Boys…etc Using one of these additives per bottle instructions and then afterwards a Nice LONG AND HARD DRIVE can easily free up the rings.
Have you “Read” the Spark Plugs lately? They have a story that they are trying to tell you I’m almost sure of it.