I had planned on running this fill for 3,750 miles, but the high dirt ingress noted in the last UOA was really bugging me. Plus, the usage instructions for the Auto-Rx engine cleaner directs users to change the rinse oil and filter after 2,000 miles. I also felt guilty that I had not had a chance to really hunt for an intake leak, nor do any other maintenance other than change the air filter part-way through this OCI.
So, this OCI was for only 2,013 miles/9 weeks. Most of the miles were from several trips up to Tahoe to ski. The roads between here and there are frequently sanded and sometimes salted and I believe that contributes to the high dirt levels in the engine, and thus the oil. The rest of the mileage came from weekend errands. I added 10 oz. of LC20 to the oil at the start, and then another 3 oz. after 1,000 miles. I also changed out the OEM paper air filter for a Purolator PureOne air filter about half-way through the OCI.
Again I relied on Terry Dyson's expertise to interpret the results, and once again it turned out to be money well spent.
When I initially read the results I despaired—the silicon still seemed quite high, and so did the iron levels. This OCI was about one third as long as the previous one, so if you multiply the wear metal and contamination levels by three I ended up in the same ballpark as before with no improvement in wear. However, Terry clued me in that wear metals do not accumulate in a linear fashion, so his interpretation is that the new air filter substantially fixed the problem. Yea!
We both were uncertain about the elevated PQ reading, however. Terry thought that maybe the LC20 was scavenging some crud that the Auto-Rx didn't get, but that was just a guess. We'll keep an eye on it and see what it does the next time around.
In the meantime I am getting the PCV and fuel filter replaced as I type this entry, so that should further eliminate any potential problem sources. (Fuel filters really should be changed every 30K miles, but most manufacturers have dropped this from their recommended service schedules in an attempt to minimize maintenance costs. I mean, who but an extremely small number of their buyers will actually do oil analysis, or consistently log their fuel mileage, and notice when the fuel filter gets clogged or otherwise starts failing?)
For the new fill I used Castrol Syntec 0W-30, otherwise known as German Castrol or GC for short. This is a thick 30-weight oil, which is a viscosity that the VQ-series engines seem to perform well with. Unlike the rest of the Castrol Syntec line, which uses Group III oils that aren't really synthetically created, the 0W-30 that is made in Germany is a very unique and cutting-edge chemistry. (See the GC oil forum at Bob Is The Oil Guy to learn more about this wonder oil.) I also added 10 oz. of LC20 again, and will add another 3 oz. every 1,000 miles.
Terry gave me the go-ahead to run this oil 5K or 6K miles before sampling, so it will probably be close to another year before I get that many miles on the truck and am ready for the next oil analysis. We'll see how the oil holds up—stay tuned!
UPDATE 2006-04-12: I got the fuel filter changed, but my mechanic wants $500 to change the PCV! He has to remove the intake manifold to get at the PCV, so there's a lot of work involved to do so with this particular engine. I'll settle for changing the fuel filter for now and only consider changing the PCV as a last resort.