I've got a 1984 Chevy van with 125,000 miles on it. It has a 305 cubic inch engine. I have been using Valvoline standard oil and change it once a year. I don't even drive the van 2,000 miles per year. Should I keep up this routine or do you suggest something else? I do get smoke when I start it up, but someone told me it is common in old small block Chevy engines. What do you gearheads think?