P420, Low MPG, Burning Oil

Hi all. I have a 2008 Prius with package 2 I purchased new with 4 miles on her. I want to keep her around for a while yet if possible but am having issues with an intermittent P420 code, low mpg, and burning about a quart of oil every 1,000 to 1,500 miles. She has 231,548 miles. Just did an oil change last night and replaced underside skids. She had a run in with a deer just about a year ago and I had to replace both water pumps as a result but otherwise just looks ugly because I have not found matching fender and hood so the fender is the wrong color and hood has the deer body impact dent still.

The P420 is intermittent and seems to come on when the oil is low or gas is very low, and goes away when these are fixed. I am still working on remembering to check the oil every gas stop (which is like every other day now that the gas bladder basically holds 6-7 gallons). So the issue may lay in the oil burning. Thoughts on where to start to diagnose? Spark plugs where changed with iridium tip maybe 10k miles ago, there were wrong spark plugs for about 15k miles just not iridium tipped. Cylinder 4 plug seems to be burned more on last two replacements. MPG is down in the 30's for the last year or two. Car is almost all highway and lifetime average MPG is just below 44 with 97.5% of fuel information obtained to get that number.

 

Thank you for the reply. Thats what I have been doing but would like to see if there is anything that can be done without costing a ton to get her back in better shape. I am fairly handy so anything I can do myself I would like to do. Any reasoning why the low oil and gas is causing the P420 code?

 

I dont currently have the tech to get the o2 sensor info, have a good reader but as far as I have been able to figure it does not read that but will check again. The oil has probably been say just more than a year, I noticed it a short while before hitting the deer. Main issue with just doing the cat is $800 quote from mechanic and I cant get under there to saw it off or weld a new one back on.

 

You are saying I am at half what is acceptable in oil consumption? Geeze. I through a quart per oil change was horrid before this started.

 

Thanks! Good to hear this report m.wynn. Unfortunately on the synthetic oil I did that about half the time for the first five years depending on poverty level at the time of oil change, but I think I always did at least partial synthetic.... Been Synthetic all the way for at least 100,000 miles. My goal is to keep her as long as my previous 17 year old Sentra so at least seven more years, but the new safety tech has me somewhat with a wondering eye, though the tech upgrade from that 91 Sentra to the 08 Prius was pretty amazing at that time too!

Of course that Sentra had a total of 173,000 miles at 17 years and I am over 50k past that already.

 

Looked into the self install on the cat, any thoughts on no weld cats? I could get that in myself! Also today the code came on, new oil still full, gas at half, normally it comes on when oil or gas is ultra low. Any thoughts on this? Any suggestions on driving style that may be adding enough to trip the sensor?