I have an '07 LBZ Duramax with 78K miles that I bought from a fellow I know. When I bought the truck, he told me it had never burned any oil and he was running 15/40 dino (I believe him). I live in Southern BC, Canada and winter temps routinely get down to 0 to -4 F with an average of 14F. I do lots of short trips in the winter and longer trips pulling an #8000 trailer in the summer. The truck does have a block heater and sits outside. Because I do lots of short trips in the winter around town I put in the 5/40 syn and over 4000 miles it burned two quarts. While this is still within the oil burning specs from GM, I just don't like the idea of burning oil. I am considering going back to the 15/40 dino. I would prefer to not get into the UOA's and extended drain intervals and am wondering if, given my location and how I use the truck, I would be putting undue strain on the truck (starter, batteries and engine) going back to the 15/40 dino oil for the winter, particularly given the fact that my winter driving is mostly short, in-town trips where the truck never really heats up. The other factor is that Walmart just had a killer sale on Castrol Tection 15/40 and I was able to get 5 gallon pails for $19.