Originally Posted by LS1121

In the old days 1960-1970 tolerances were not as close as they are now. Running thicker oil would be OK not desirable though. I remember putting "Motor Honey" in my old 283's because the parts were worn. My LS1 still has the stock bottom end in it and I still use 10-30 Mobil1 with over 308,000 miles on it. Unless you live in fairbanks or someplace in Saudi Arabia I would just stick with the manual says. After all GM did design the motor they know what it needs. lol contrary to what some experts believe.