I have used Castrol GTX 10w 30 for approx 20 years,i have 2 cadillac sts,s with 32 valve 300 hp engines in them.The one cadillac has over 250,000 miles on it with no engine troubles,the other cadillac has over 170,000 miles on it with no engine troubles either.I also have a silverado Z71 with...