I would like to get some knowledgable and experienced responses on the topic of high mileage oil, such as Castrol GTX Hi-Milelage oil. I have a 99 TL with 98k miles and am wondering if I would get any benefit or see any adverse affect from using said oil. Any views on this out there? Thanks.

My mechanic told me once you get to 100k you SHOULD use a higher grade oil. That's probably true for any car. Higher viscosity!