changing the filter ever 3kmi is NOT very useful with synthetic. a lot of what the filter catches is viscosity improves, etc as mineral oil shears down and decomposes after 3kmi. syn fluids don't have this problem with such short drain intervals. i change my 15w50 and filter every 7500 miles. mobil 1300s and chevron del 400 are better than rotella and even slightly cheaper. comparing heavy duty diesel, direct injected trucks with 44 qt sumps, multiple filters, and run at 1700 rpm (redline 2400) to indirect injected MB light-duty diesels than ran 2500-5000 rpm is not a good idea.