This 1978 Paymaster truck was completed in November of 1978 after 18 months of design and construction. The vehicle is the third generation of the Paymaster design and was the twelfth vehicle built. This truck has about 850,000 miles on it.
 
 This was the first of the vehicles with a sleeper cab and also the first with tandem rear axles. The tag axle was used in place of a tandem drive axle setup because it has slightly lower friction losses due to not having another prop shaft and gear set. This helps reduce the engine loads and is a positive factor in achieving better fuel  mileage.
 
 This vehicle uses a single crossflow radiator up front with a variable speed fan that is powered by an aircraft hydraulic system. This also conserves horsepower.
 
 Another maintenance feature on this truck is that it has no accessory belts on the engine. All the accessories are powered by direct mechanical or hydraulic drives.
 
 Over two million dollars was spent in developing and testing the Paymaster truck design and there were over twenty very detailed and scientific testing programs that the vehicles underwent. These tests included such things as wind tunnel tests at the University of Maryland, scientific ride analysis by Bostrum Seat Co. and scientific structural analysis by A. O. Smith Co.
 
 Detroit Diesel Allison, Cummins Engine Co. and Firestone Tire Company also conducted lengthy and detailed testing on the vehicles. In one test, a second generation truck tractor was driven 24 hours a day, seven days a week on the Firestone Tire Co. test track at Fort Stockton, Texas. It was run a total of 39,295 miles pulling loaded double trailers at a gross combined weight of 109,000 pounds at 60 mph.  The results of this test was that this Paymaster truck got 19.8% better fuel mileage than a Mack truck running at a gross weight of 107,000 pounds.
 
 Improvements in fuel mileage were the result of reducing the demand horsepower on the engine at normal operating speeds. A standard truck of the period required about 235 hp. to run 55 mph and the Paymaster design with reductions in aerodynamic drag and  rolling resistance, along with reductions in the accessory loads, cooling fan power and friction losses  was reduced 100 horsepower to only 135 hp at 55 mph with the same payload. Along with these reductions in horsepower demand on the engine, the proper gearing had to be chosen so that the engine operated at its most fuel efficient RPM at the desired cruise speed.
 
 Two examples of fuel mileage comparisons of this third generation Paymaster demonstrated substantial savings.
 
 One test was a comparison between the Paymaster and a cab-over International Harvester on a run between Portland and San Francisco. The Harvester used 340 gallons of fuel for the round trip and the Paymaster used 240 gallons for the same trip at the same loads and speeds.
 
 A large fleet in Chicago used a 1980 Paymaster on a run to Davenport, Iowa. The Paymaster saved 55 gallons of diesel on each round trip compared to their fleet tractors.