1994 Honda Civic (auto)
1.
5L I-4
~33MPG on highway trips
1998 Lexus ES300 (auto)
3.0L V-6
23-24MPG on a former work commute of about 35 miles per direction (appox 60% highway).
1999 Mazda
MX-5 Miata (manual)
1.
8L I-4
It has fairly short gearing and obviously isn't made for the highway.
~26MPG highway cruise (top down, closer to 30 top up)
~20MPG driving briskly on secondary roads
2002 BMW 330Ci (manual)
3.0 I-6
~20MPG on the trip computer but I live about 5 minutes from work and take a lot of short trips. This consumption figure probably represents about 30% highway driving.
All of the above figures are realized while operating in significantly undulating terrain. Much of the highway driving with the Lexus was done on a stretch with 1 mile+ climb intervals of significant grade.