that is better MPG with that Datsun than many of the small cars get now.
I wonder if this is a result of emissions standards?
That's at least part of the reason.
Case in point: My first car was a '73 Grand Am, with the smogger motor that barely ran. Got 10 MPG initially . . . but when I applied the techniques of a publication called "The Emission Control Bypass Manual" the fuel economy went up to 12.5 - 13 MPG, with greatly improve driveability and a significant power boost.
A friend with '75 Valiant Dart with the 6-cylinder engine experienced even more dramatic gains when he did the same to his vehicle . . . and he had a box with around 50 lbs. of parts left over!
Today's engines and emission controls are
far more sophisticated than they were in the '70s, but aftermarket chips and other accessories are available for many vehicles which will improve power or economy, sometimes both, but always at the expense of emissions. That tells me that emission controls
do exact a price in fuel economy.