Prius (2010-12) :: Oil Consumption At 136k Miles - Too High

The oil consumption started around 90-100k miles. My wife mostly drives the car so I just check it and fill it without keeping track of mileage. Last week I had a lot of driving to do so I topped off the oil before starting my trip and put a 5 qt 5-20w bottle in the back. I've been through two liters in 2100 miles! Sheesh - I'm ticked off. I do my own oil changes at least every 10k miles, always use 0-20w or 5-20w full synthetic oil (usually Mobil 1). I replaced the spark plugs at 119k miles per maintenance schedule.

Besides the oil consumption, since 115k miles the engine can get into a mode where it misses a little bit at low power once it is completely warmed up. I have a good code reader and nothing ever shows up. I expected the new spark plugs would fix it, but they didn't change anything about how it runs. It is slowly getting worse. I'm going to wait until a code in the ECU is set before fixing it. It could be an ignition coil. I suspect it is an O2 sensor which causes the AFR to be too lean which makes the mix hard to ignite. Time will tell. It runs fine when cruising at highway speeds.

We bought this 2010 Prius III, not 3, new in October 2010. The only out-of-the-ordinary thing we do is live in northern Wyoming where it can be very cold for a long time. We drive 85 mph for long distances to go shopping and visit friends. The gas mileage is the same as it has always been. It varies between 42 and 50 mpg in the summer and 35 and 45 in the winter.