All On-Highway Truck Engines
The specifications for the fuel setting and high idle are given in Fuel Setting Information. These specifications have a tolerance that is also given in the Fuel Setting Information book or microfiche.
Some servicemen make adjustments to the high side of the tolerance, even when it is not necessary. For example, the static fuel setting specifications have a tolerance of ± .15 mm (± .005"). For a specification of 3.05 mm (.120 "), the adjustment would be correct from 2.90 mm (.115") to 3.20 mm (.125 ").
It is important to remember that adjustments to the high side of the tolerances can cause a reduction in fuel mileage [km/L(mpg)]. On some engines this reduction can be as much as 0.09 to 0.13 km/L or .2 to .3 mpg. This will not be acceptable to many customers, especially those who have economy series engines.