Ralph, in cold weather, you will never get the good heat from the vents from a low speed, low rpm, 3 mile drive. Ever. That’s because the heater core is displacing the not so hot coolant from the engine.

He's letting it warm up for 15 minutes before each drive and with only 3 miles of travel its a real calculation.
When we had that last cold snap I was in the 8mpg range with the same work drive and warm up procedure. Mine doesn't sit in a heated garage either

Chevrolet gives you a $1,350 credit for buying the Turbo Max 4-cylinder engine it is listed on the window sticker.

On the next truck, get heated seats and steering wheel, and you'll barely notice if the heater isn't working. ;) Heated steering wheel is the thing I miss most when I drive my old truck instead of the new one.

Honestly, you'd probably save a lot of gas as well, since you wouldn't need to let the truck warm up for 3X longer than the actual drive... just hop in and go, you'll be warm in a minute.

They don't offer heated seats & steering wheel on a work truck. I don't let it warm up before driving it is parked in an unheated garage

On my dealer's lot is a black standard cab short bed 1500 with the TurboMax, only engine available in it I'm told. Really cool truck.
I've had two TurboMax owners tell me they love the power it has.

We bought one (4 cyl) for work a couple years ago when you couldn't find anything full size with a 5.3 in it anywhere. If I recall the 4 cylinder actually has more torque than the same year 5.3. Guy that has it says it has plenty of power compared to his old 5.3. Only real issue is the other guys razzing him about driving a 4 cylinder truck.......and it sounds a little wimpy. We don't really track the mileage so not sure about that.