on a ton-mile-per-gallon basis than the US average for Class 8 (36t gvw) trucks. Further tests to demonstrate its capabilities in daily operation are planned for later this year
Engine oil was Rotella T4 NG Plus 5W30 oil, an FA-4 fuel-efficient engine oil for high-temperature, high-shear operation. The transmission oil was Shell Spirax S6 GME40.
Drive axle ratio was 2.85, which was set to optimise fuel consumption in the highest (12th) gear at the local 60mph speed limit.
Predictive cruise control helped improve the efficiency of the 12-speed Eaton Endurant HD automated transmission.
The tractor, a custom-built lightweight carbon-fibre frame, rides on a custom long wheelbase, sitting on an LT International donor chassis (from M-B brand Navistar). US trailer builder Spevco carried out the conversion. Two CNG tanks are mounted at either side of the tractor.
The overall coefficient of drag was 0.25. To reduce weight, the Starship tractor chassis moved from a 6x4 to a 6x2 Meritor FUELite chassis, saving 300lbs. It runs on Bridgestone 295/75 R22 load range H tyres.
The roof is fitted with a 5kW solar array to support auxiliary systems.
At highway speeds, panels automatically deploy to cover the gap between tractor and trailer (but not so tight that the truck can’t change lane).
With significant forced air intake through the front grille, cutaways behind the wheels force out that air (and exhaust). They also channel air along side skirts to minimise turbulence underneath.
The 16.5m trailer rides on Bridgestone GR-03 R195 Ecopia tyres, covered by full-length side skirts. A customised boattail completes the rear. The 20.7t payload of Shell Rotella oil (in crates) was distributed in such a way as to make the most of axle capacities.