I have a 1995 toyota paseo...?

WHAT! who told you it was a piston ring and obviously its leaking outside the engine for you to say its a really bad oil leak. i would take it to a reputable mechanic shop and get a second opinion, it looks like you're about to get ripped off if you are not careful. and second of all if you have a bad piston ring its very costly to repair because that would entail getting the engine rebuilt and being a toyota from my experience rebuilding engines, is not cheap. good luck.

if it is the piston oil ring then yes it is hard to repair because the engine must be overhauled to replace them, but the rings themselves are quite cheap

here is a way to tell if you have a blown oil ring on one of your pistons: let the car idle and check the exhaust and if any black smoke is coming out then yes it probably has a bad oil ring on a piston or two, if none came out @ idle then get someone to goose the throttle and if black smoke comes out than you have a oil ring that is going bad

but if you put a peice of clean cardboard under the car after you park it and come back in a few hours and check the cardboard and if it has a sizeable oil dot then you just have a bad leak. Just check the oil regularly and keep adding if needed. **NOTE** this is not a fix to the problem, but it will keep the car running as long as possible

I have never jump to the pistons rings.

they are,almost never, the culprit.

Do a compression test. if all the pressures are almost even,then replace the valves rubber gaskets.

by the way,oil leaks is one thing,burning oil is another one.

I assume ,You are talking about, burning oil.