Unless there's a mechanic who can refute my statement(s), a plugged CAT does not result in higher oil consumption. Backpressure in the exhaust results in loss of engine power because it cannot "breathe".
Two ways you can check for a plugged CAT:
1:) Hook up a scanner which can read the voltages of both the upstream and downstream O2 sensors. Go on a road trip preferrably on an expressway, and maintain a steady cruising speed. If both the up/downstream O2 sensors are switching from high to low in synchronicity, the CAT is not doing it's job and is either clogged, damaged, or on its way bye-bye.
2:) If the engine seems to lack power, remove the upstream O2 sensor(s) and drive again. If the engine seems to have more power, then the excess exhaust pressure is escaping thru the hole you temporarily created by removing the O2 sensor. You'll have to disregard the loud roar of the engine by the unmuffled hole where the O2 used to be. Similarily, if you remove the upstream O2 sensor, start the engine, and there's a LOT of exhaust venting out the hole (before you even take a road-test), the CAT is likely plugged.
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Tuesday, February 17th, 2009 AT 9:35 PM