Driven Racing Oil 01806 - Joe Gibbs Driven BR Break-In Motor Oil
$7.99 a quart from Summit. Or use another brand of oil strictly developed for break-in. It doesn't cost any more, or just a little bit more. Use the right tool for the job!
Why mess around with regular oil with additives that might fight each other, or Diesel oils with very high detergent levels that prevent the ZDDP from sticking to the parts?
I also don't understand the 20W50 oil after break-in. Maybe you should just pour some gear oil in because it's thicker? Remember that the oil has to be thin enough to get into very small clearances.

R.