I just got a 2020 Chevy Silverado with a 3 liter Duramax.

I bought it for the mileage and size.

The truck has almost 3,000 miles on it.

It is a 4x4, mostly highway driven cruise set at 60 mph.

The mileage was around 22 mpg for the first 2,400 miles.

It has gotten as high as 34 mpg but as low as 7.9 in the city.

It has dropped in half overnight with ten minutes warm-up.

I am interested in performance upgrades that will not void the warranty.

Also have seen how almost no one has aftermarket products out there.