I have not bought any lately to notice a scarcity - but I have not been looking.

I use Rotella T6 in my diesel tractor and diesel lawn mower, and in my motorcycles...and sometimes in my RV and Jeep when in the hot summer and I am going on a trip and will be towing something. (When cold weather returns I go back to the 10W-30).

I use a lot of Rotella T - so I buy it in 5 gallon buckets when they have it on sale.  The last time I bought some was at Rural King and i bought 10 gallons.