I tried to match my recommendations to the type motor you have...I consider an 8.1L V-8 a super heavy duty application and I wanted to recommend oil and filters more than equal to the task, not just good enough. The Mobil 1 filters are well-built and have a great filtering capability but I think they are more restrictive in terms of oil flow. Would I use them, yes, but I think you can do better. The K&N is well built, is burst resistant to higher pressures and I believe has a better flow rate. I have never used a Donaldson but my understanding is they are well built, only experience about 1 PSI differential between input and output pressure and are designed for long change intervals. I think they would be great in an application such as yours. They are available through truck/industrial equipment parts places. Since I posted my first answer, I have decided that Mobil Delvac 1 5W40 might be a good oil for you...if it complies with your warranty requirements. I would definitely consider it if warranty were not a player. While it is a diesel oil (your motor is a gasser, right?) I think it might be perfect for your application, again assuming it meets your owner's manual viscosity recommendations while you are under warranty.
[ July 28, 2003, 12:03 AM: Message edited by: pscholte ]