I buy it by the 5 gallon jug. It's $42 a gallon, or $27 for a 2. 5 gallon jug. . quite a bit of difference in price! I will not run synthetic, and change my oil faithfully every 2500-3000 miles in both trucks. When I drove a 379 Pete with 670,000 miles on a 3406E, we changed the oil every 10,000 miles, instead of 15,000. . It did not smoke at all, and oil analysis was very good. IMO, I think the extra cost is not worth it...
-Chris-