40k in the original example is the mileage I put on my car on average during a given year. It is not an oil change interval.

I don't buy into the Amsoil 25k oil change. It CAN happen under ideal conditions, but even with amsoil, your engine ( even the best engine with the best oil) will burn oil. I would expect that at least 1 quart (likely more) filler quart would be used under even ideal conditions. Oil usage in a typical engine can range from 3k to 14k (on the same engine one 2.5l duratec compared to another 2.5l duratec). The issue with Amsoil is that they use the same additives as the rest of the industry and they will rarely last as long as their claimed 25k miles.

"If you are flammable and have legs, you are never blocking a fire exit" -Mitch Hedberg