Why do Corolla's burn oil?

One of the common problems with older cars is that they burn too much oil.

I took apart a 1ZZ-FE Corolla engine and explained why they burn so much oil and made a short video on it:

The two main causes of engine oil burning are piston rings and valve stem seals.

Here's a break down of the engine's piston head and its rings:

The problem on many cars is the engine runs hotter than it was designed for, causing the petroleum inside the oil to break down and cause sludge and carbon buildup. The carbon blocks the oil return holes in the piston head, and the oil that's scraped off the piston walls has no where to go, except up, into the combustion chamber, where it gets burned!

Here you can see on my Corolla with 200,000km the carbon building up behind the oil control ring:

Here is the three parts of the ring - that center springy part is supposed to be free and easy to move, collect oil and allowing to drain into the piston head. Instead it just gathers carbon and clogs up.

The second way cars can burn oil is valve stem seals.
Valves separate the well lubricated top half of the engine from the combustion side of the engine. The seal between them will get dry, crack and leak after many miles and heat cycles. This causes oil to pool onto the pistons overnight, causing blue smoke at startup in the morning:

There's no easy preventative maintenance you can do to stop the piston rings from getting carbon buildup. The ultimate solution is to drill more holes into the piston to allow more oil to flow through the rings, but that pretty much requires an engine rebuild!

For more on engine oil lubrication, see my video and thread where I explained how it worked here:

Hope it gives you some insight. Enjoy!