Gene K

Im not necessarily arguing with earlier changes if you feel safer with that and are not willing to do analysis. I am however arguing that its better to base them on the IOLM instead of a set mileage or time. Change at say "60% Oil Life Remaining" instead of 3 months or 3,000 miles. Their is also the option of upgrading to Full Synthetic (which last significantly longer) as your "Safety Margin" and following the IOLM.

I dont doubt oil degrades over time when not in a sealed bottle in climate controlled conditons.

However pretty much any oil that meets API SM will not degrade significantly just sitting in an engine in 12 months or less.
At least according to any evidence Ive seen.

Ive seen Mobil 1 0W-40 that was getting close to the lower limit on TBN at around 48 months but that could just as easily have been from the 18,000 miles as the 4 years.

Once you get out their past 18 months I start to worry about the filter. If its synthetic media its likely fine but paper makes me nervous much past that.

What convinced me that extended drains are not that detrimental was 1.25 million miles on one of my CAT 3406E Diesels using 30,000 mile OCI with conventional oil. Admittedly it has a much larger sump but not that large for an engine putting out 1650 lb of torque, getting 6 mpg, running at much greater average power loading and dealing with soot loading. It took a lot of analysis to convince me.

Now race oils without detergents are a whole different ball of wax as they are not able to neutralize the acids formed during normal operation.