[Big Dave]

Read the avatar text. My Impala is the old B-body Impala, not the glorified Cavalier sold as an “Impala” today. EPA Combined: 19 MPG.

The truck’s net double overdrive ratio is 0.57:1.
The car’s single OD is 0.71:1.

The Cd is like most Cds posted here – a guess.

My route is one third urban/suburban, one third two-lane state roads, and one-third Interstate.

The car has relatively LRR Goodyear Assurance fuel Max tires. OD = 27” The truck has OEM-spec E-rated Firestones. OD = 31.7”