main bearings shouldn't only last 60,000 if treated right they should last closer to 200,000 then again it is a Chrysler product...... i personally wouldn't run too heavy of an oil in there..... lighter oils actually coat and move better than heavy oils do.......which is why a lot of a manufacturers are using 5-20 now...... i dont really know if i would reccomend running an HD 30 in a tired motor