3.9 Liter V6 Swap

Gina Grahame said
I bought a new '92 Dakota Club Cab, 3.9, 5 Speed, with a 3.55 rear and i would get 28mpg on the highway. Had for 7 years, no real issues.

HOW???? I don't see that as possible to get that good out of a 3.9 in a Dakota. occasionally I hear 22-23 but never 28.