The GM 2.8L Dmax going the Colorado is not an Izusu original design. GM, up till 2013, held a 50% share of VM Motori in Italy. I had a 2.8L VM Diesel in a 2006 Jeep Liberty. I have done a lot of digging around and looking at the 2.8L Dmax, and except for a different brand VG turbo, a little higher rail pressure, a little more hp and torque, it is a carbon copy of the VM 2.8L, except the latest emissions stuff. Would make sense, VM builds good motors, and I am sure GM already started working on their 2.8L while still owning a part of VM. The GM 2.8L going in the Colorado has already been in pickups elsewhere in the world. It isn't something novel or new.
My experience with the VM, is that is was a great motor. Cast Iron block, wet sleeved, DOHC and it would pull like a bull. It had no problem yanking around a 300 gallon fuel wagon around hilly, soft farm ground. I pulled a class 6 Interstate Battery truck out of the ditch with it during an ice storm shortly after I got the Jeep. And the EPA estimated highway mpg for it was 27 mpg, and there were very few times it averaged less than 32 mpg on road trips.
And the 2.8L is developing as much or more torque than the small blocks in the 1500 series pickups, except the 6.2L. And it is doing so at 2000 RPM compared to 4200+ RPM like the V8's. People get stuck on horsepower but that isn't a diesel's forte. My 12.7L Detroit 60 in my semi only has 500 hp, but it has 1750 torque and has no trouble pulling around up to 80,000 lb running at 1425 RPM. A Dodge Viper has considerably more HP, but it would blow up trying to do the same work. Sure gearing, chassis, and drive components are different, but if you took the Viper motor and put it in a semi truck and made everything else equal, you would have pistons and rods going thru the oil pan trying to pull 12,000 lb of trailer with 46,000 lb of cargo in the back. HP and torque have different relationships between different fueled engines.
Fuel pricing is as much relative to states as it is to regions. State fuel taxes are all over the map. In Iowa, right now diesel is averaging 30 cents a gallon cheaper than regular gas. Great for my trucking operation!
I think, for the typical buyer that would get a mid sized pickup like the Colorado, the 2.8L diesel would more than make up for it's additional purchase price over it's life cycle. Most folks who get something like this would rarely pull more than 6000 lb behind it, would not be trying to load a ton of concrete in the back, and would most likely use it as a daily commuter vehicle to work. The 2.8L would shine in those situations. I am not giving up my 2015 2500HD for one, and am not in the market to have another pickup around, but if I were, I would take a very strong look at the Colorado with the 2.8L Dmax.
