I am interested in this discussion. when I bought my 06 Patriot with the C13 525 hp, the filter guage was at 19" of water. So figuring maintenance was behind I changed to the C15 air filter. no difference. Went on a 3 k trip and the filter gauge went to 22. (No off road)
Having several over the road trucks I have never seen this until many miles into the normal maintenance cycle.
So I when it warms up I am going to run a prescribed path that will exercise the engine.
1) air filter as found
2) air filter with the snorkel disconnected drawing air from the engine compartment
3) if weather allows, no air filter at all, short distance up the 3 % grade we have nearby
It makes no sense to me. But want to understand it.
I plan on replacing the muffler with the aero turbine 5050xl as this cat is anemic compared to my OR C12. also adding a new Raycor filter at 125 gph with a prime pump.
So I hope we can share data
Larry H
2006 Patriot Thunder
Cat c13 525 hp