If you are going to extend your drain intervals (as I believe you can) with synthetic, you must still change your filters. As SW mentioned, I drain my Amsoil diesel synth. every 10,000 mi., but change filters at 5K. With many types of non-automotive filters, they become more efficient as they become loaded (such as HVAC filters), as effective pore size is smaller. Yet when they become very loaded, little passes through. It is very different, however, with automotive oil filters.... as the filter becomes clogged, less and less oil will go through filter media, travelling instead through bypass ports, unfiltered. Just think of it....if a car oil filter becomes totally clogged, oil is still circulated through the engine...it just travels through bypass ports in the filter and not through filter media. So dont leave filters in for 10 K, especially on a diesel. You could change filters at 3K, but I decided that 5K was OK as this is the manufacturer's recommendation. Also, I think it is important to use an oil formulated for diesels...soot inhibitors, etc. Furthermore, make sure your air filter is in good shape to minimize oil contamination with dust...I use K&N (but I'm not sure if this is the wisest choice) regular OE paper filters may be best. Finally, if you do a lot of driving on dirt roads, more frequent oil changes are in order. Myself, I drive mostly hiqhway miles.