this is a tough subject because there is alot of disagreement.
Porsche recomends 30k miles between oil changes and filter changes every 15k. (Porsches use 10 to 13 quarts of oil)
Mercedes was 15K on oil and filters every 5k.
Honda is 15 and 5
BMW was 10 and 5.
MB and BMW are now using FSS that moniters run time, mileage, and temperature to recomend when oil changes are due.
The thing to remember is the manufacturers want to push oil changes back because it lowers the yearly cost of ownership. This number has become more and more important as a selling point so anything they can do to lower this number, they will. Oil changes dont bother them because descent oil is going to do ok and by the time there is a problem, you are out of warrenty.
In my car, I run mobil 1 synthetic for 10k miles with no filter change in between. My engine has 170k miles on it and I have no sludge or problems so far.
