Constantino; glad to hear of your positive experience with stretching your oil change intervals. Performing oil analysis is certainly a good check on your engine minder. It is used extensively on expensive industrial equipment to OPTIMIZE the drain interval.

Oil drain intervals are a function of vehicle engine condition, use and climate. Please indicate what your driving pattern is and what you local climate is like. I would not want a reader in Minnesota who parks his Vokswagen outside in the winter without a block heater to go 10,000 miles between oil changes.

My own experience on a small block Chevy (with no blowby) with normal dino oil was that at 3000 miles of summer driving the total wear metal count was 60 parts per million (ppm); compared to a "condemn level" of 200ppm as per EXXON/Mobil guidelines. Additive depletion was about 50%. Viscosity was in range. Total Acid/Base number was in range. This would indicate that summer driving would allow 6000 miles or more on the same oil.

However, winter short trip driving creates contaminants in the oil without depleting the other qualities of the oil. I don't trust the computer to catch blowby, soot and condensation.

A few years back GM's research division published a paper on measuring oil life chemically by using acidity as the measure. It worked very well, but such a system is expensive to install and tricky to keep operating properly for the life of the vehicle. The computer simulation is cheaper and more reliable, but may not be accurate for all situations.

Since oil is cheap and engines expensive I would use the more frequent intervals to ensure the maximum engine life.

Others have addressed the oil issue. You asked also about coolant and transmission fluid.

My BMWs do not specify change intervals for coolant, and they say that the tranny fluid is "permanent". Sure it is..... That sounds good to a new buyer, but unless you want to rebuild the tranny before it hits 200k miles, I suggest replacing the tranny fluid every 50-100k miles, depending on how you drive the car.

I replace the coolant and brake fluid every two years in all four of my cars. Two of my cars are past the quarter-million mile mark.

I tend to replace the oil a bit more frequently than the car display suggests. The wifemobile that uses synthetic oil would go ~10k miles if I followed the indicator. I do it at about 6k