I have a 1999 EX with 190,000 miles. I have run Synthetic Mobil1 5w-30 at 5000 - 8000 mile intervals for most of the oil changes. It uses no oil and leaks no oil.
I have also had some changes with non-synthetic 5w-30, and currently have Motorcraft 5w-20 in the van. I have read the Motorcraft is a semi-synthetic to obtain the 5w-20 rating. I notice no mileage / performance / noise difference with the 5w-20 vs. 5w-30.
For my next change, I will either use the 5w-20, or go back to Mobil1 or synthetic Pennzoil 5w-30 in April as warm weather in Texas starts early in the year.
If there are no leaks, and it is using no oil, I do not believe the high-mileage (or synthetic) oil would be necessary. I use synthetic because of the hot summers here.