2008 Toyota Prius - Codes and oil consumption

278,000 miles. Burns 1/4 to 1/2 quart every 3000 miles for the past 100,000 miles but seems not to be getting any worse. Car runs great. started tripping engine codes 0420 (cat converter) and 0456 (small evap system leak) at the same time (within a few days) in the late fall. I’ve been resetting codes looking for pattern for when they trip. Only it seems as it is getting warmer again outside it is getting less frequent. no codes for the past ~1000 miles. Any ideas what this is? Seems quite a coincidence the cat and evap system would go bad within a few days of each other. Can one problem cause both codes? mileage and power completely normal. car runs great. Any ideas or experience with this? Thanks!

With the 278,000 miles, and the P0420 code I would change the O2 sensor after the CAT
One of the very few O2 sensor codes where replacement would be my first choice, especially with the high mileage.

The P0456 could be as simple as a failing or loose gas cap, again with the age and mileage, I’d just replace it.

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Thanks for the O2 sensor idea. I’ll give that a shot. As for the gas cap thanks for that too but I forgot to say I already changed it but it didn’t fix it. I even bought the genuine Toyota parts version from the dealer to be sure, but no go.