Y'know, this does bring up an interesting point.
I'd be interested in running a full synthetic for a long period of time IF I was able to filter it extremely well, both to get out the micro particles and soot. I haven't yet found a good(bypass) filter that can do that; it almost seems like you'd need a centrifugal filter, but those are kinda expensive.

edit:
Also, why 10W40 for a turbo engine? As long as you have sufficient oil flow, the 15W40 should do just fine, especially warm. At -20F, you might have a problem with lubrication, but you'll have the same lack of lubrication at those temps everywhere.

 

Mac, guy i work with has an 01 cummins, has the oil sampled etc. Running 30k on dino with a bypass filter. His is the paper type, i want to say .2 micron. He told me the reports always say he can go longer, but he said 30k just seems like so long lol. Its turned up to 300/700 and only uses it for hauling heavy loads, so it does alot of sitting too.

 

What filter model? This is the important bit.

 

I will try to remember to ask him. Going to borrow his trailer at the end of the month

 

I use dello 400le 7 quarts and four quarts 0-40M mobile 1 full synthetic, it is one of the few synthetic that meets Mercedes warrantee requirements gas and diesel.. with a mobile 1-601 filter, its a power stroke filter and is a duel filtration 18 and 5 micron and is slightly larger than IDI filter and will fit under my van..