I have always use Rotella F6 5W-40 in my Spyders and recently went out to purchase a couple of gallons to do a needed oil change in my 21 RTL. I went to 4 Walmart's that were all out of stock. Then I went to every auto parts store in the Myrtle Beach SC area who either did not carry Rotella F6 or were out of stock. Well, there is always good ole Amazon.....Wrong! They told me they were "temporarily" out of stock and gave me a February "tentative" ship date. Not sure what's going on at Shell. So, I have 2 questions..... 1. Is anyone else having this availability issue with Rotella and 2. Recommendations for an equal substitute? Thanks for your input guys.