My Sterling 9500 with a C9 engine and 294k miles is down with bad cylinders 3 and 6. Caterpillar claims the rings are completely worn out and therefore no warranty coverage even though it has engine warranty to 500k. They claim the C9 engine is not suitable for the application. If that is so why did they classify it as an on highway engine? Why did they sell Sterling however many dozen/scores they sold them for this application? Why are who knows how many trucks doing similar work with even C7 engines? This is a 33k gvw truck, not an 80k semi. Any input on how to get Cat to do the right thing will be appreciated.