Throughout reading here correct me if I'm wrong but the 4 cyl piston rings are known for being faulty causing the oil consumption issue. Say I bought a 4cyl cheap with low miles for a good price, if I replaced the piston rings with oem or even upgraded rings would this fix the issue for say another 100k miles?

 

Oil consumption issues can depend on the year of engine as piston design changed.

The original issue appears to be the oil return holes in the oil ring grove of the piston plugged up with carbonized oil plus perhaps low tension rings. The result was increased oil consumption. Toyota's fix was newly designed pistons, assumed with larger holes and and more of then, and new rings.

Later on Toyota apparently incorporated pistons with oil spray holes which may have added to the problem.

Some DIY types have cleaned the pistons and drilled out the carbon plugged holes.

After a repair, use only synthetic oil and change it more often then stated in the owners manual. The oil apparently breaks down with usage and plugs up the holes which contributes to the problem.

This engine also had issues of head bolt threads pulling out of the block. The block was later redesigned. If your doing a rebuild consider this issue. Time-Serts can be installed to fix this issue on a DIY basis.