[gone-ot]

Found this interesting reading:

https://cumminsengines.com/uploads/d...el_economy.pdf

...especially their summary:

Rock-Solid Rules
 Every 2% reduction in aerodynamic drag results in approximately 1% improvement in fuel economy.
 Above 55 mph, each 1 mph increase in vehicle speed decreases fuel economy by 0.1 mpg.
 Worn tires provide better fuel economy than new tires, up to 7% better fuel economy.
 Used lug drive tires can get up to 0.4 mpg better than new lug tires.
 Ribbed tires on the drive axles provide 2–4% better fuel economy than lugged tires.
 Every 10 psi that a truck’s tires are underinflated reduces fuel economy by 1%.
 The break-in period for tires is between 35,000 and 50,000 miles.
 Tires make biggest difference in mpg below around 50 mph; aerodynamics is the most important factor over around 50 mph.
 The most efficient drivers get about 30% better fuel economy than the least efficient drivers.
 Idle time is costly. Every hour of idle time in a long-haul operation can decrease fuel efficiency by 1%.