Greetings all. The previous owner of my '86 300 SDL and I have ALWAYS used Delvac 1 (5-40w) synthetic engine oil. He ran low average miles on the vehicle while I STRUGGLE to get 2,000-2,500 miles a year on the clock now. I have been changing the oil twice a year but am wondering if I am wasting money (at $20/gallon) plus filter, time or labor.

I am completely sold on using Delvac 1, but wonder if I can get away with an ANNUAL oil and filter change. Any insights you can offer are appreciated!