[Meeni]

Hey all,

My car is exhibiting poor fuel economy. Sometime I drive it in a way that calls for punishing fuel economy, but even when I drive in a sedated way, it remains on the low-end of the scale.

MY average, doing mixed highway/city driving (commute, but not stop&go) is 18mpg. It is lower in summer than in winter (I can see up to 20.8 in winter, which is not great but significantly better). It used to average 24mpg a couple years ago, on the same type of commute cycles.

The car is a 330i, 120k miles, running on Shell 93. It has a leaking valve cover (yes, again...). No codes. Acceleration feels strong, although not as impressive as I remember it once was (possibly psychological). Tailpipe gets some soot, nothing crazy, but it does. Plugs, oil, air filter etc have been replaced recently. O2 sensors and coils are original.



I know that vacuum leaks and dying O2 sensors can all cause poor economy, opinions on a course of action ?