I just got back from my trip to the Outerbanks and realized that I've already put 3kmi on my fill of M1 0w-40 and 15w-50. With 4 quarts and a turbo would it be a stupid idea to go 10,000mi on this fill and do one UOA at the end of the run?
Man, that was a fast 3k! It's only been about a month, hasn't it? I'd say it partially depends on how quickly you roll up the next 7k. If you'll complete it before winter, then I don't think there's any concern that you're stressing this robust mix.
Although, for the first time going this long, it might give you peace-of-mind to pull a UOA sample at 5k mi & swap in a new filter, then do another UOA at the end. That's what I'm doing on the 9³ right now. Then, when I'm convinced that the oil's doing well, I'll just go the entire interval. But my 9³ doesn't use any oil in 10k miles, so I get a little more comfort by adding a bit mid-way. Does your 900 need any top-ups? That could help it out quite a bit.
I think on any oil the limit should be 7500 unless you have done a UOA to see how hard your engine beats the stuff up. I would not go 10,000. I went 7500 on one oil and did and UOA and found that 7500 was too much for this synthetic. I am trying another systhetic and will do a UOA at 6000 to see whats up.
Eiron, I might try that one out. It doesn't use any oil at all (knock on wood with 123kmi). I was expecting some usage with the full syn, but it hasn't used a drop. BTW-the 10w-40 in the trans is awesome. I was having a problem with the syncro for fifth (I had to give it a good pause or it would grind) with the drive clean it's shifting perfectly.
Hey! Where's everybody else on this one? I certainly expected a bunch of input here. How 'bout you's guys with Swedish (Volvo/Saab) turbo experience? A quick search of the UOA section shows a ton of turbo owners. C'mon! I know you're out there!
The other great thing about doing a UOA before you start extending your OCIs is that it helps you catch weird stuff going on. My first UOA let me know that I had a antifreeze in my motor oil, albeit at trace amounts.
As a result, I postponed my plans to run an extended OCI until I could verify that my engine was in good running order.