Bragging? Very odd that you would think that was what I was doing. I am just relating a satisfied customer experience. My experience was with cars and light trucks, and they are not designed to last as long as heavy duty trucks such as the one you drove. But my oil change interval was 25000 miles in most cases (except for my current F350 where it is 10,000 miles. ) I also use it on my tractors with a 200 hour interval. When I had a diesel Suburban, I once ran it to 30,000 miles and then drew a sample and had the oil tested. It met the viscosity, base number, detergent and anti-wear additives expected on a new oil, though I am sure all were depleted to some degree. The main change was high soot loading, which I attribute to the fact that the Suburban diesel was a really crappy engine.