2007 oil consumption and oil smell

At the end of 2018, I noticed the smell of combusted oil coming from the tailpipe of my Prius. I first noticed it from inside the cabin whenever I'd stop at a red light, presumably because the vapors wafted into the ventilation air intake. I'd also noticed my oil consumption was increasing, and had been ever since I passed the 100k miles mark (about a quart every 5k miles.) When I took it to my mechanic, he replaced the PCV valve and changed the oil with 5W30 synthetic. Ever since I bought the car brand new, I've used 5W30 dino oil, so the move to synthetic was something new.

Since then the combusted oil smell has persisted. I don't see blue smoke coming from the tailpipe even in below freezing temperatures. It's also not an oil leak inside the engine comparment because that would be a different smell.

My question is: What could be causing so much oil to be burned, and is there something other than using heavier oil or additves (like Lucas Oil products) I should be looking into? Is it time to look for a rebuilt engine? Thanks in advance.

 

Thanks, audiodave. That's correct: No red triangle of death or any other warning indicators.

 

Yes, even when the car has been driven for 20 minutes or more and the coolant has reached 186ºF, it still has that smell. It happened last summer and continues now that it's winter.

 

Yes, spark plugs were replaced at 120k miles, which was 18k miles ago.

 

No, the exhaust system is tight. The mechanic said so, and I did the old ‘over the tailpipe with a rag while the engine is running’ trick and it seemed to maintain pressure.

 

JC: Thanks, I'll clean the MAF and throttle body. I appreciate your advice.

Prius_Angie: Thanks for the recommendation. The cabin and engine filters have both been regularly replaced at recommended intervals. There are no leaves in either air intake.

 

@Mendel Leisk: Yes, always good to check the basics. The cap is on snuggly.

 

Just to put a button on this thread, it turns out my exhaust manifold was cracked and needed to be replaced. That wasn't a fun repair to pay for. (Just over $1K.) But that's what was causing the foul smell when the car wasn't moving. Because the manifold is underneath the cabin air inlet, the fresh air setting would draw the leaking exhaust vapors into the cabin. It was so rich that I erroneously identified the smell as that of burning oil. While both the mechanic and I initially felt like the exhaust system was without a leak (rag-over-the-tailpipe test), a closer inspection revealed the cracked manifold. It has since been replaced and the smell is gone.

As for the oil consumption, it seems to be a lot lower. I know if has nothing to do with the cracked manifold, but I did run some Sea Foam in the crankcase for about 500 miles before the last oil change. While I haven't quite put 5K miles on it since the last change, the reading on the dipstick is much higher than it had been. According to what I've read (on the internet, so it must be true), the rings on various Toyota models tend to get clogged, which can result in noticeably higher oil consumption. Running the Sea Foam in the oil before a change is supposed to knock the gunk out of the rings. I'll post more complete results the next time the oil is changed.

Thanks for everyone's help,

MattLTH

 

The engine is more quiet now. I think the manifold crack must have opened gradually and the increase in engine noise crept up slowly. It was never really loud, just different. I wish it had been louder because that would have prompted me to take corrective action sooner.