Synthetic 15-40

[toad]

I have a 1996 7.3. I have been running schaffers synthetic in it. I change it every 7k like they say to do. I am just wondering if it is worth the expense?Or should i go back to just running rotella in it?

Also how often should the fuel filter be changed?

[Aussiekeeper]

Keep using the Schaeffers, it is very good oil. Change it every 10,000 miles if you use a by-pass oil filter. Have been using the 9000 synthetic for years....