Miles are 80-90% highway. The car sees full throttle every morning during the first 30 seconds of start-up. This sample was taken by the dealer at the 30k service. The air filter on this fill was the original, and was not dirty at all. This is the car's oil change history to date: 3k: Mobil 1 0w-20 SN, supplied oil to dealer 10.5k: Toyota 0w-20 SN, bulk, by dealer 15k: Mobil 1 0w-20 SN, supplied oil to Luscious Garage 20k: Toyota 0w-20 SN, bottled, by dealer. 30k: Toyota 0w-20 SN, bottled, by dealer. The sodium is odd since none of the previous oils contain a sodium additive. Perhaps this is contamination from a dirty funnel? The coolant level has remained stable and has not dropped, so I am not too concerned about it. I think I will stay with 10,000 mile intervals for now. Unfortunately, this means it will take me a long time to get rid of the 31 quarts of Toyota 0w-20 I have in-stock.