Smartway is a program from the EPA that is supposed to help truckers select tires that have better Rolling Resistance (the way tires can be measured) for better fuel economy.
Review the information provided and you will see that most truck/bus tire companies have a line of tires available that meet the Smartway standards.
Will selecting one of these tires get you 20 mpg on your 40' DP No it won't but it might get you a 5% improvement which could be like getting $ 0.15 off a gallon of fuel which
I bet anyone would like.
While we are on the topic of fuel economy here are some tips from RVTechLibrary
ß Every 2% reduction in aerodynamic drag results in approximately 1% improvement
in fuel economy.
ß Above 55 mph, each 1 mph increase in vehicle speed decreases fuel economy by
ß Worn tires provide better fuel economy than new tires, up to 7% better fuel economy.
ß Ribbed tires on the drive axles provide 2–4% better fuel economy than lugged tires.
ß Every 10 psi that a tire is underinflated reduces fuel economy by 1%.
ß Tires make biggest difference in mpg below around 50 mph; aerodynamics is the
most important factor over around 50 mph.
ß The most efficient drivers get about 30% better fuel economy than the least efficient
ß Idle time is costly. Every hour of idle time in a long-haul operation can decrease fuel
efficiency by 1%.