I put Rotella T 15W-40 in my car right after I bought it. It was recommended that I use this. My cars oil probably had 20 or 30K miles on it.

There is a post here with a photo of the oil filter I removed, that actually had a huge hole in the side of it where it had been on there for so long. It was grotesque.

When it hits 1000 miles, I will change it again, but want to go to a different grade of oil, that will have the maximum pressure when the engine is hot. What grade would that be? 20W-50?