Very odd consumption issue

[Torrid]

So the Jaguar has had its off and on leaks which I've replaced seals to fix and the Lincoln has had some weird consumption problems. I'm curious your opinions on what might be happening here. First a bit of background. The Lincoln was my late father in law's car and sat mostly, barely being driven for three years. It was always serviced at the dealer and I'm assuming based on this Motorcraft 5w-20 was the oil used. When we first got it just over a year ago, we drove the car from the Midwest to Nevada where we live. I'm not sure why I didn't think to check the oil level during the trip, but it was right at the minimum level when we got home. Knowing it had been recently changed I wasn't sure if it just wasn't filled to max, I topped it off with some Mobil 1 5w-30 I had sitting around. For the next three months it absolutely drank oil. It felt like I was adding a quart every few weeks and it wasn't driven much. I changed the oil to Edge 5w-30 thinking going up a grade may help. If it did, it was negligible. This car is severely short tripped, mostly used for the 2 mile drive to and from school by my wife for our daughter. It's used once a week for the grocery and shopping run and that's its longest trip, about 25 miles total. When she started working again for a bit and the trips were longer the consumption flat out stopped. When she left the job, the car went back to barely being driven. Fast forward to last week and the check engine light came on for an upstream O2 sensor and the car went to smelling like raw fuel on cold starts, so I replaced the bad sensor and I drove it for three days to make sure everything was good. I put roughly 150 miles on it and raw fuel smell disappeared, but in this time the oil level dropped from full to the midway point. Finally after 9 months at only 3,800 miles duration I decided to change the oil to PYB 10w-30. During the 3,800 mile OCI I probably added around 3 quarts. Now I don't think the oil will make a hint of difference but I'm wondering if the O2 fueling issue could be the reason for consumption coming back? I mean if it was getting a large amount of fuel dilution and heating it up to burn off the fuel by actually driving it, could that burn off some oil in the process? I know a few will suggest replacing the PCV but the Lincoln 3.9L V8 doesn't have one. One thing is for sure, I'm back to watching consumption like a hawk.

 

[Yup]

Isn't this a mechanical maintenance topic? But, to answer the question, I have no idea but doubt 02 sensor would lead to oil consumption.

 

[Torrid]

Possibly. It was causing fuel dilution.

 

[abycat]

The vehicle my wife drives which is now the nissan always was and will be short tripped for the most part. About once a month it does 200km and up trips. I always use a syn 5w30 which the 5w30 part is what's recommended in the manual. Also severe service with a nissan is pretty much 99% of people and climates. It doesn't burn or leak anything so short trips alone can't be a big concern but fuel dilution from problems and overfueling issues can cause big issues like ring wear and cyl bore wear. I would try a high mileage oil in both your vehicles and cross your fingers that it helps. I know I would have to either 100% fix or get a new car that didn't burn any since the wife couldn't be adding litres of oil on road trips.

 

[Torrid]

The Jag definitely doesn't need high mileage. It used to burn some oil for some reason when using synthetic. It's now squared away with no leaks or burning at all, but I still have my concerns with the Lincoln. Sitting has wreaked havoc on it. The rear brake calipers were completely frozen up when I replaced the brakes. At 12 years old and only 56k miles it needs new front bushings at all points and new front bearings wouldn't hurt. There's a hint of noise from them.