some cars are more aerodynamic and such, that front airdam helps a lot too if you have one.

I'd think the A14 MT4 would get the best mpg, but who knows, datsuns always got good mpg when driven reasonably.

the factory mpg for the 81 210 (sunny 310 whatever ) with A15 MT5 was around 28 +/- 2 can't remember if that was city or highway, but i think city.