A quick search on "oil" revealed at least a dozen threads in the past twelve months on the topic of what type or grade of oil to use in a Stoveblolt. Of the dozens (perhaps hundreds)of recommendations, it seems that 10W-30 came in first with 15W-40 (usually Rotella) a close second. There were also many votes for straight 30 and 10W-40, with a smattering (one or two) of votes for 20W, 20W-40, 20W-50, 5W-30, and Mobil 1 15W-50. There was one recommendation for a blend of 3 quarts of 30 and two quarts of 10W-30. I may have missed a few. I did not see any votes for 20, but there still seems to be some confusion over when to use, or not to use the "W" after the grade number.
There were many (but not quite 50%) recommendations for a ZDDP additive, even after break-in.
I only noted about three recommendations for a non-detergent oil, with several for synthetic.
I use 15W-40 Rotella, with EOS, in my 261.
Hoyt
