Your truck is rated by the EPA at 21 city and 22 highway. Look it up at www.fueleconomy.gov. It was never rated at 28 mpg.
He is in Canada. Yes it was - rated higher actually 29mpg in Canadian FE ratings which use a different test protocol than the US. Numbers used to be almost identical north and south of the 49th, but when the EPA changed the test protocol a few years back, US FE ratings dropped. Remember we use an imperial gallon which is 20% bigger. The US numbers would still be 24/25 just with the size correction.