When I bought my 04 Sprinter, the printed dealer hype mentioned that it could go up to 20K between oil changes on synthetic oil, if it had a specific computer upgrade (assyst?) on it. My invoice sheet lists this option, but none of the dealers that have serviced the vehicle claim to ever have heard of this.

I use synthetic oil. The truck has 56 K miles. Nearly all my mileage is long trips (300+ miles at a time). They reset the computer every time its changed, they claim, to 10K miles. As I watch the count-down mileage, it invariably tells me that I have considerably more miles left than would be shown by the oil change sticker. I've gone as far as 17,500 before it zeroed out.

The most oil its ever used has been one quart between changes. Am I runing the engine, or am I using it like it was designed? Anybody have any thoughts on this?