Factory 2.1, Volkswagen Vanagon GL Campmobile, 4 speed manual transmission.   Hankook 195R14 tires.

Highway driving, I try to maintain 60 mph, I may go faster if necessary to be
safe in faster traffic.

At 60 mph, 3400 rpm, generally 20-21 mpg, depending on conditions.  Has varied
from 16 up to 24.  The lower figure is from trips in windy conditions, when I may slow down some, too.   The
higher figure turns up at high elevations in rolling or level, not steep, terrain.

These figures are not adjusted for the slightly oversized tires, but the difference for 195 vs 185 should be very little.

David McNeely