First, thanks everyone for your help. It's hard to know what's working without looking inside the engine, but I bought the car at 60k and it now has almost 120k. I'm not sure if it was well maintained previously, but I started right away with full synthetic. Toyota specifies 5w30 so that's what I used and I switched to high mileage at 75k.
My mechanic said 10w40 would protect the engine better especially here in Florida, but I'm skeptical so I asked here. Also, it looks like Pennzoil only makes 10w40 in a non Platinum version and I thought the Platinum might be helpful as well. Last, the engine uses about one extra qt of oil every 5000k miles. Any further suggestions with this additional info? I wouldn't think 10w vs. 5w would make much difference?