I would say the test mules with over 100,000 miles are probably past break in. These engines are beating the oil up pretty bad. I would suggest not running any oil, regardless of basestock, past 5000 miles. There's a lot more to an oil performing function than TBN. I would question the value of any oil regardless of basestock that has sheared from a 5w-30 to a 5w-10. Yer truck, yer money.