|
what do your spark plugs look like?
use Google Maps or Mapquest to calculate % Hwy driving (im sure u can figure that out using MS Excel) ... and what speed/rpm do you usually drive at on the highway?
what rpm are you at if youre cruising at 60mph? 70mph? 80mph?
when your car first starts - is the exhaust visible, even when its warm out? is it visible after the car is up-to-temp?
no leaks? oil looks good? coolant looks fine and is proper level?
... trying to give you some things to check, because 21mpg is enough of a drop to be a recognizable problem
|
