Originally Posted By: UltrafanUK
.... a lot of detergents that have a nasty habit of cleaning off some of the very important anti wear layer deposited by the old oil far faster than a new layer can be baked on by the new oil. So oddly enough if you do a series of different OCI's you might well find nearly as much wear occurs during a 3000 mile OCI as a 5000 mile one (Most of the wear is during the first 1000 miles).....
You'll have to explain to me how those detergents (Calcium, Magnesium, Sodium, etc.) do that "over-cleaning." If you look at most of the UOA's presented on this site, you will notice that the detergent ppm levels from a VOA to a "used up" UOA don't vary by all that much. By the UOA you end up end with 90-100% of what the VOA originally had. So I don't see how that slight difference accounts for significant wear in the first 1,000 miles vs. the last 3,000-11,000 miles.
What if those initially high wear rates are also related to a dry oil filter on initial startup? Or contaminants in new oil that have to be slowly filtered out/burned up during those first 1,000 miles? Or maybe that fresh oil helps to "unstick" formerly bound contaminants that were already buried in the engine....and came out with the fresher oil, and were not just from fresh wear? Or maybe stripping the old protective wear layer is especially true if you're switching oil brands where the add packs are quite different (ie say Pennzoil vs. Valvoline?). A lot of people use different brand oils every OCI.
SAE paper from 2007
This paper demonstrating less wear on a 15K mile Las Vegas fleet suggest that the first benefit of lower wear occurs as early as 3,000 miles as the TBC films at 3K vs. 15K were similar. The next question is who is going to push their OCI out to 10K-15K miles to take advantage of this lower wear at the expensive of excessive thickening/depleted TBN, etc, especially if their owner's manual suggests 3K/5K oil changes? What if your climate is a lot colder than Las Vegas?
TBC films vs. fresh/aged oil
Best summary of the above by EdHackett: "This paper is often cited as proof that running your oil longer results in less wear. The paper does not say that at all, and that conclusion can not be drawn from the paper. The experimental design was not set up to test lower wear in an engine."