All of my above questions were rehtorical questions with obvious answers. I have the answers, and the testing data. You're saying that you are saving money by running your oil and doing UOA's every 10-15K. If you go by Amsoil's recomended change interval for diesel's of up to 50,000 miles or longer with UOA's then you will be doing 5 UOA's by then. Lets say that you find a good sale on your oil and filter and you change it for $50 then you do your 5 UOA's at $20 each. Now at the 50,000 mile mark you are at the $150 mark, if your oil even lasts that long. Now at the 50,000 mile mark I've spent about $110 plus $20 for my first UOA, and $20 for a filter for a total of $150. You didn't say when you change your filters so I didn't include them in your total, but if I did you can see the results. Now in that 50K I've enjoyed better fuel mileage and easier cold weather starts and increased protection without having to do the 5 UOA's and multiple filters all the while having a warranty to back me up. Now in real life, very few people will do either of these. I don't know where you get all of your information, but I'm not new at this and I do have published tests from multiple sources and multiple UAO's from my trucks. I used to run Rotella, and had many many miles with it. I always did UOA's and changed it before I needed to. I had hard starts in cold weather and just figured it was a diesel thing. I changed to Rotella's so called synthetic and it was a little better, I tried several other brands "synthetics" and they were really no different than Rotella's "synthetic" until I tried Amsoil. I noticed a difference in how quiet it was, and it smoothed the idle out, and I got a little better fuel economy. I was excited about that, then it got cold again and the truck started like it was 50*. The truck no longer did the lope when I started it in 20* weather and I maintained my fuel mileage from warm weather. Now you can say whatever you want to about Amsoil or any other oil out there, but Amsoil does make a superior product and I've lived it through 3 trucks now. Maybe it's not woth the extra $ up front for you to justify it, and I'm not trying to sell you on it, but through experience and research I can say beyond the shadow of a doubt that Amsoil DOES have something special about it!

Doug

Shell Rotella T 15w 40 with one quart of Lucas oil treatment and a Cummins brand oil filter is all i have ever used and in my eyes is the only kind to use A++ stuff i hope this information helps out!!

I use Amsoil, for fairly obvious reasons. I've got about 20k miles on this last change with just an amsoil filter (no bypass). I am about ready to do an oil analysis on it to see how it looks, then I will probably change it, just because.
Scott