Cat C-7 diesel oil viscosity

I have a document from cat entitled RV recommendations. It is dated 6-07. For the C7 the recommended oil change interval is 11,000 miles or one year. There is no mention of hours or fuel used. Those are for off road and stationary engines. However Jaugston is correct that a lower interval is a better practice. The C7 uses the infamous HEUI system and dirty oil will kill it!! Remember this is one of Cat's worst ever powerplants. I cannot provide a direct link to the document but do as follows: Google: " Caterpillar LEHT9288-06 (6-07)". The first hit is for the cat RV club. Click on it and that document will appear. Very informative. I am going with 7500 miles or one year. Anyone who thinks you can go 20,000 miles is nuts! Using synthetics is a total waste of money unless you live in Alaska. Today's diesel oils are light years ahead of the oils from as little as 10 years ago. They mimic synthetics without the added cost.

Moisheh