I have an '04 Corolla that just turned 200K miles. Since I've owned the car I've done 6K OCIs and it's never used a drop of oil between changes. About 6K miles ago I did my last oil change and I found some full synthetic (Havoline) on sale that made it basically the same price as the dino I normally use, so I thought what the heck, why not...nothing wrong with throwin in some of the good stuff once in a while, right? And, I should be able to go 10K on this OCI because full syn is good for longer OCIs. Well apparently, this engine doesn't like this oil, or the oil doesn't like this engine because it was a quart low when I checked the level. I've never had an engine of mine go from zero oil usage to using a full quart in one OCI just from switching from dino to syn...have any of you ever experienced this? I'm hoping the engine will go back to zero usage once I switch back to dino...