excessive oil consumption with a new 2018 Toyota Highlander 6 cal

Ask Toyota but I doubt this is enough to trigger a warranty repair. If you are using 0W20 oil you may want to switch to 5W20.

Yes, contact the dealer service department to make an appointment and get it logged as excessive. Then you and they can will watch the consumption over time to determine if you have a real issue.

Check the area around your timing chain cover as there are numerous complaints about this. There is also a Toyota mechanic on YouTube that shows you where to look for the problem

This is an issue with a major problem in Toyotas 6 cylinder engine in the 2018 Highlander. When my Highlander was new, my oil warning light went on and had to add two quarts of oil after the first 5,000 miles. Since then it has burned, leaked, pushed through oil to the point of adding 1- 2 quarts of oil every 5,000 miles. I have a 2012 camry that uses the same thin oil, and have never had to add a drop. Toyota dealership in Cheboygan, MI said that this is normal and acceptable for 2018 Highlanders. It sure as hell is not acceptable to me, as i bought this vehicle so my wife would have a rather new and trouble free vehicle to drive if something happens to me at my age. She , now, will have to be checking her oil every so many miles, to make sure her car does not burn up. At her age, what a nice present to the elderly. Toyota and their dealerships should be ashamed of themselves