Toyota Repair: losing oil, worn piston rings, charcoal canister


Question
QUESTION: Hi Ted, My 2003 Toyota Corolla CE now has 100,000 miles and I change my oil every three months (about 2,000 miles).  At oil change, my dip stick indicates I am down about 2 quart of oil out of 4 quarts total.  There are no oil marks on my driveway.  The result of Toyota's testing of 4 trouble codes indicated I need a new charcoal canister, fuel filler neck and gas cap which would cost over $1,000.  I declined.  Everyone I ask recommends a different oil and thickness.  I have been using conventional non synthetic 5w-30 oil and recently changed to high mileage 5w-30.  Some people tell me to try 10-30 or even higher if that doesn't help.  I have been told that losing 1 out of 4 quarts of oil during oil change is normal.  Other than checking and adding oil as needed, are there suggestions you can offer.  Thank you Ted.

ANSWER: That oil consumption is way too high, one quart per 1000 miles is the maximum acceptable level, I don't understand the reasoning behind recommending a charcoal canister etc, it may solve the check engine light issue but it won't help the oil consumption, may be if you can give me the actual code numbers I can have some suggestions for you.
These engines are known to use oil to either leaking valve seals or piston rings, if you are getting blue smoke at cold start then it's the valve seals, if not then the engine is burning the oil due to worn piston rings.

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QUESTION: Ted- There is no blue smoke at cold start.  At over 100,000. miles, I suppose I just need to monitor the oil level.  I have no idea how many miles these vehicles usually last.  Can you suggest what indications I can expect in the coming years which would indicate planning for a replacement vehicle?  These four diagnostic codes were provided to me 8 months ago. Po440, Po441, Po442, and Po446. Would using a higher numbered oil such as 10w-30 be of any help with the loss of oil? Finally, what is your recommendations on using products like Sea Foam motor treatments which are added to the gasoline for the purpose of cleaning engine parts.  Every year I have the standard 3 step fuel system cleaning performed so I am not sure if using products like Sea Foam have an impact on the longevity of my engine.  Thank you for your forthcoming answers to these concerns.

Answer
Hello, the four diagnostic codes indicate a leak in the fuel vapor recovery system, commonly called the evap system, although it is possible that the charcoal canister is the problem there are possible other reasons such as a leaking fuel cap that is not sealing the system or a disconnected hose or malfunctioning switching valve, since a Toyota dealer tested and recommended the canister I would be inclined to accept their diagnosis. Using a heavier grade oil should improve the oil consumption, other than reading online about the seafoam product I have no personal experience in it's use, some people do report good results, in my opinion the fuel system cleaning every year is not necessary, maybe every three years.
I recommend that you monitor oil consumption by filling the oil to the max level, drive the car 1,000 miles and check the level, add oil to bring it back up to full and see how much it used. Feel free to reply back to me with your findings.