The only way a Suburban gets 12 mpg is if it's towing something as big or bigger than it is.
TRY 20 MPG on the highway and 15-16 mpg in town.
If Suburban and Tahoe only managed 12 mpg my service drive would be loaded with angry customers..My Escalade AVERAGES !! 22 mpg on hiway !!! 16 in town.
You must be thinking about the all powerfiul TOYOTA Tundrs 10-12 mpg.