Replacing engine and catalytic converter...

I went to a "new owners night" at our local dealership, with the Service Manager shepherding us around. At one point he intoned: "Our goal is to make it so you never need to pop the hood". Ugh...

Second gen oil change interval in the States was 5K miles or 6 months, whichever comes first. And I believe there would be a caution, saying if you do various detrimental things (like lots of short trips, excessive idling, extreme low temps and so on), to cut those intervals in half.

Suddenly with 3rd gen, the engine and/or oil's twice as good?? For 3rd gen in Canada, Toyota still said 8K kms (5K miles) or 6 months, fwiw. With 4th gen they're in lock-step with the States.

Bottom line: make up your own mind about this. Engines and Cat's are a lot pricier than a few extra oil changes.

There is another reason for excessive oil consumption though: Toyota, in their quest for high mpg status, used low-tension piston rings. They cause less friction (improving mpg), but don't do as good a job keeping oil from migrating up into the combustion chamber. The TSB for excessive oil consumption entails replacing both the pistons and rings, tacit admission.

 

Toyota's part number for the complete assembly including the catalytic converter, exhaust heat recycle system (EHRS) and the resonator is 17410-37300. The variant without the EHRS is 17410-37160.

You can find a MagnaFlow equivalent for the latter at AutoZone or O'Reilly's, but you most likely have the EHRS variant. This can be confirmed by the presence of additional hoses going into and out of the assembly between the second cat and the resonator—refer to the attached diagram and look under the car on the driver's side.

If you need to replace the catalytic converter having the EHRS, you have two options:

1. cut off the original cat before the heat recycle system and replace with an aftermarket offering, such as the MagnaFlow 52455 (this will likely not be an option if the EHRS has been hacked away at by thieves), or
   
2. replace the complete assembly with the OEM part 17410-37300. I am not aware of any aftermarket equivalents for this part number.

I have no experience with the MagnaFlow cats; I mention them only because they have the correct renders on their website and detailed instructions on the repair.

 

As another data point in your decision making process, evaluate the "do nothing" approach.

Purchased in bulk, quality oil is a little over $2 quart.
At one quart every 300 miles, it would cost $200 to drive 30,000 miles.

On the plus side, you probably will save money on oil changes, since it will be a constant oil change.

Someone smarter than I am can opine on whether the catalytic converter is related to your oil consumption, but in Colorado spending at least $715 in emissions-related repairs gets you a waiver. And you can often find a repair that is needed anyway, which is related enough to "emissions" to qualify.

Good luck!