Something I heard about MPG

[Klint]

A bud that I have never cought in a lie (meaning I dont think he would lie). But he was talking about his friend got a new truck I think like a S-10.. He got home and drove it for about a week and his gas gage didn't really move much so he went and filled it up and ran it for a few days (about 300 miles) and it still didn't move much, he then went and filled up his truck again and he figured up his MPG which was around 76..... He didn't think this was right so he went to his dealer and the dealer removed a chip and he is now getting around 25.. What... Do the car makers have a deal with gas companys or is this just a tell from the camp fire.