I don't have my burb on the road yet and it is running a 67 250 (for a while anyhow) put in place many many years ago. So I can't answer your question but I can tell you my experience on the grocery getter. Manufacturer recommends synthetic on a 7500 mile change cycle. They do say that if you use regular oil you need to follow a 3000 mile change. For that reason alone the synthetic is a good value.
