I have a neighbor that has a GMC Sierra 1500 AT4 crewcab shortbed with the 3.0 Duramax.
He had a Silverado 1500 crew cab short bed with the gas 5.3.
He says that the 3.0 beats his 5.3 in all categories.
It's quicker pulls way stronger and gets insane fuel mileage, just about as good as I got with my Colorado Duramax.
He said he gets about about 26 around town not towing or hauling anything and upwards of 32 on the highway with no problem.
I believe him. I was going to buy one but at the time it was actually rated to tow 500 lbs less than our Colorado was.
Didn't make sense to me but that's what the original rating was.
Now the 3.0 is rated to tow the same weight as our 2019 GMC Sierra crew cab standard bed which has a 6.2 and 10 speed auto.
If it had been rated that way when they first came out I would have gone with the 3.0.
But I'm happy with the 6.2 it's quicker than some of the muscle cars that I owned and worked on back in the day.
And gets around 22 mpg on the highway empty running at 65 mph. And I can get 18 around town in light traffic.
I think that the auto stop fuel management system helps it achieve the city mpg.
If I'm running the AC cold, it drops to around 16 mpg because the auto stop doesn't engage and shut the engine off at lights.
Amazing how a little extra idling drops mpg.
Anyway if anyone has any experience with the 3.0 I would love to hear about it.