Car is losing oil

Consider adding a small bottle of dark purple dye to the oil, then check a few days later with a black light. The dye will show up as a bright yellow stain. If the oil is sneaking past the piston rings, the dye will show up inside the tail pipe. Auto parts stores will have the dye, and those that rent or borrow tools should have a black light.

Be aware that it is considered normal for any engine today to use some oil between oil changes. To address the huge number of complaints, the dip sticks are no longer marked with "full" and "add". They now say, "min" and "max". Some oil change places just barely fill the oil to the "min" mark and consider that good enough. With that, you can expect the level to be too low very soon. If you start out near the "max" level, you should be able to lose about a quart and a half before it reaches the "min" mark. Even then, I would not be too concerned if you are getting close to the next scheduled oil change.

I used to lose about a quart of oil every 1,000 miles on my 1988 Grand Caravan. The engine went over fourteen years and 150,000 without an oil change. I just added a quart every 1,000 miles, which kept the additives replenished, and I changed the filter when I was I the mood, about once every other year. I started out doing that because it sounded like the engine was about to expire, but I ended up getting over 420,000 miles out of it before the body rusted away so badly, the carpet was the only thing holding the front and rear together! That was abuse, not neglect, but it showed what some engines are capable of. There were times I let the oil level get so low, it did not even reach the dip stick. Rattling of the engine was what told me to stop ignoring it.

At the mileage you listed, using more oil is not uncommon. If you find dye inside the tail pipe, the solution is to replace the piston rings or the valve guide seals. Replacing the piston rings is a major job on any engine, and is not a good value. You are better off just adding a quart of oil between oil changes. Valve guide seals are fairly easy to replace on a lot of older engines, but special tools are needed for most Toyota engines. For that reason, changing those is probably also not a good value.

Also, be aware that changing to synthetic oil often leads to leaks. I have seen two cases where large leaks developed shortly after the owners switched to synthetic. In at least one case, when my student switched back to regular oil, the leaks slowed down a lot after about two months, but it never completely dried up. The issue seemed to be the synthetic oil, but there is something else to consider. Every brand of oil has its own blend of additives to include detergents, dispersants, anti-foaming agents, corrosion inhibitors, and seal conditioners. Many of those additives are not compatible between different brands of oil. The detergents in the new oil could neutralize the seal conditioners left behind from the old oil, and lead to leaking seals. That would not affect the sealing of piston rings, but it could lead to leaking valve guide seals. People who stick with one brand of oil seem to have the least oil-related problems. I used only the cheapest farm and home store stuff I could find for my Caravan, but I stayed with that brand every year.