which is best, new or old type oil

[Good Ole Bob]

It's time for an oil change, and last night I went over to the local Wal Mart for soem. I have been using Rottila T, and thought about switching over to the new scintheic Rottila. The new stuff is 5 W 40, and the old is 15 W 40. What is the difference? Has anyone tried this new oil, and how do you like it. Thanks

 

[Pit Bull]

I use the old 15w40 Rotella T and will stick with it. It was good enough for the 1,000,000 plus mile Dodge CTD featured in the Registry, most be good enough for me. By the way the 5w40 just flows better in cold temps.