If you added an aftermarket cam take the advice regarding break found thereon on the cam card.

20 or 30 wt hd oil. EOS (1 qt of EOS Engine Oil Supplement) found at Chevy Dealers. Follow the directions.

Then after a few oil and filter changes switch to a 10w30 synthetic if you like.
Tim grin

"Drugs are money, money is power, power is security." - Kent Heiner
Nedrow population 2212
Carbon footprint family of 2/11 tonnes of CO2/yr