Originally posted by ScottK: I'm curious, for those who run extended drain intervals with any oil (say over 5k miles) - what does your new oil look like say 3 days or so after the oil change? Does it look exactly like it came out of the bottle or does it darken up immediately?
My main concern with extending drain intervals is that even if the lubricating properties of the oil are fine that it may saturate with "gunk" and start letting conaminants fall out of solution and form sludge deposits. Quick darkening of new oil is an indicator that the old oil could no longer hold all the crap in solution, leaving the new oil to pick it all up. I know that regular 3000 mile changes with run of the mill mobil leaves my oil looking brand new for weeks after the oil change.
I use Mobil 1 every 5k now because its so much easier and cheaper to find, but in the past I used Amsoil series 2000 0w30 and did extended drain intervals of 10k with only a filter change at 5k. My oil looked perfect the entire time, I had even sent it in for analysis once after my normal 10k and it was clean enough for another 5k easily. In my old 914 I would run 20w50 for 12k with no problems and that car was really hard on the oil.
