lifetime fuel savings
(4) Lifetime fuel savings For purposes of this subsection, the term “lifetime fuel savings” means, in the case of any new advanced lean burn technology motor vehicle, an amount equal to the excess (if any) of— (A) 120,000 divided by the 2002 model year city fuel economy for the vehicle inertia weight class, over (B) 120,000 divided by the city fuel economy for such vehicle.