SLS wrote:
Your missing the point!
The superior quality of AMSOIL synthetic motor oil doesn't brake down like DINO oil! A 100% synthetic motor provides the ultimate in protection and performance in your CRD. You need to keep synthetic motor oils free from dirt that is what causes engine ware.
Recommended Sampling Frequency for the most comprehensive analysis possible on diesel engines is 100 - 500 hours or 3500 - 20,000 miles.

First, you need to go back to school and better your word spelling.
Next, I have taken diesels to almost 1.5 million (yes MILLION) miles on dino oil and doing 30,000 mile OCI's (no bypass filtration). Amsoil and other high end synthetics are good, but they are not the great cure all for what ails an engine. The pricing variable for the results is not worth it for a lot of individuals. Most of the motoring public turns over car ownership far and away a lot sooner than the engine will wear out anyway.
Keeping oil clean? Isn't that what bypass filtration was designed to do? There are a lot of examples in transport trucks of oil change intervals going to over 100,000 miles on dino oil. Synthetic oil will "dirty" up just as fast as any dino oil. Soot does not favor or disciminate against any oil. The additive package used will make the difference more than whether an oil is a synthetic or dino.
I have personally run Amsoil synthetics, Schaeffer synthetics, and other thru various semi trucks, with not enough beneficial results to continue the practice. In some engines, a Group IV synthetic like Amsoil will actually increase lead corrosion in bearings. Not because the oil is not lubricating, but because some bearing metalurgy is suseptable to corrosion with a PAO based oil. So, I have settled on a Group III (40%) and Group II (60%) synthetic blend from a regional supplier under their own label, for around $9 a gallon. The base oils are from the largest base oil supplier in the world (Motiva) and one of the largest add pack suppliers (Infineum). Various brands use these same suppliers for their oils and the pricing at the consumer level is usually based on nothing more than the label on the bottle. Oil samples are as good or better as any that I had with the higher end full synthetics. Same is true for my CRD and other small engines. There is no real appreciable changes in metal wear numbers, TBN retention, and viscosity changes between the various full synthetics, synthetic blends, and straight dino oils.
All those LAB test results are neat on paper, but in the real world, they usually don't exhibit that great of a differentiation in performance.
I really have no concern over what someone decides to buy, it's their money. All of the major oil brands (and most of the lessor known brands) will provide adequate lubrication for all but the most extreme operating conditions. The full synthetics are darn good oils. But the lessor synthetics and blends usually perform just as well in real world environments and cost substantially less. But, of course, brand loyalty seems to be based on a feeling more than actual real world testing. And that's ok too.