Oil change interval exceeds time recommendation not mileage - now what?

i just bought a used 2006 scion xB (owned in Phoenix by a nice old lady since new) with only 14k miles in immaculate condition. I thought I had a gem, but I discovered the oil change history exceeds manufacturer time recommendation of every 6 months: changes occurred at 7 months, 17 months, 8 months, 15 months, and 11 months. Mileage recommendation is every 5000 miles; oil was changed after 2000, then 4500, 1500, 2800, and 3600. i read that oil oxidizes over time and if left in the engine for longer than recommended and used on short trips causes internal engine deposits, corrosion and sludge? If I now change the oil more frequently than recommended will it remove any such bad stuff? Should I be worried? Thank you. Doug

Don’t worry. None of the past change intervals was long enough to cause a problem. You still have a gem.

Follow the oil change recommendations in the manual from now on and enjoy your xB.

Granted, 17 months is a long time, but the engine is young, and it will survive. I seriously doubt there’s been any long-term damage.

The horror stories you’ve been reading are over-hyped, and probably meant to sell you something. Something you don’t need.

I have a car that sometimes doesn’t get driven much, and when this happens I change its oil once a year. I’ve owned this car for more than ten years and it continues to run perfectly.

In your case you should be fine. Motor oil oxidizes very slowly. The time recommendation is largely irrelevant today as additives have stabilized the oil so much that 5000 + miles really is a good number. Time is not a huge issue at this point. 17 months was a bit long but not enough to be an issue. Oxidation is now more an issue for cars that idle long periods of time, but they are on a severe service schedule which this car probably does not meet.

It appears that it was changed often enough that (hopefully) any sludge issues will not be much of a concern.
The fact the car is from a dry climate area instead of a humid one is also a plus.

If there is any concern about sludging this could be verified by removing the valve cover and inspecting the valve train. One could also run a heavy wire (piece of coat hanger, brazing rod, etc.) probe inside the oil pan and scrape the bottom a bit during the next oil change. If the wire comes out with a trace I would not be alarmed over that. If it comes out with a gob of goo on it then maybe.

I would not orry at all about this. If this had gone on for 100k miles, then maybe, but not for 14k.