At Walmart I was looking at the Delo diesel oil and the Delvac. It says its approved for gas engines also. What are the main differences between these oils and regular gas engine oils? Is it the detergent package and less breakdown of viscosity? Also, I understand that diesel oils have sulphur or some other cleaners that can harm catalytic converters. Does this mean it would be fine to use in a pre-cat car? I keep reading on here that the diesel oils are very high quality, dont break down in viscosity as quick, and have a lot more cleaning agents in them. My 406 small block is pretty fresh from a rebuild, but for future reference I would like to know if it truly is OK to use diesel oil in a gas car, cat equipped or not.